HBSE Class 10 Science Important Question Answer 2025 – HBSE Solution

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Class 10 Science Important Question Answer for 2025 Chapter-Wise 

HBSE Class 10 Science Chemistry Important Question Answer 2024-25

HBSE Class 10 Science Chapter 1 – Chemical Reaction and Equations Important Questions 2024-25

Q1. What do you mean by combination reactions? Give one example. Most Important

Ans –  In this type of reaction two or more reactants are combined to form a single product.

Example- CaO + H2O →  Ca(OH)2 + Heat

In the given example calcium oxide and water combine to form a single product, calcium hydroxide.

Q2. What do you mean by displacement reaction? Give one example. Most Important

Ans – It is a type of reaction in which a more active element displaces less active element.

Example – Zn + CuSO4 → ZnSO4 + Cu. In this example zinc displaces copper from copper sulphate solution as zinc is more reactive than copper.

Q3. What do you mean by decomposition reactions? Give one example (chemical equation).

Ans – In this type of reaction single reactant is breaks down to two or more simpler products.

Example – CaCO3 → CaO + CO2. In this given example calcium carbonate is decomposed to calcium oxide and carbon dioxide on heating.

Q4. Why does the colour of copper sulphate solution change when an iron nail is dipped in it? Give chemical equation for it.

Ans – Because when an iron nail in a copper sulphate solution is dipped, iron replaces copper from copper sulphate solution forming iron sulphate.

The colour of blue coloured copper sulphate solution changes into green.

Chemical reaction : Fe(s) + CuSO4 (aq) → FeSO4 (aq) + Cu(s)

Q5. Write the balanced chemical equation for the following reaction:
Aluminium + Copper Chloride → Aluminium Chloride + Copper

Ans – 2Al + 3CuCl2 → 2AlCl3 + 3Cu

Q6. Fat and oil containing foods are packed with which gas and why?

Ans – Fat and oil containing foods are packed with nitrogen gas to prevent them from oxidation.

Q7. Why should Mg ribbon be cleaned before burning in air ?

Ans – Magnesium is a reactive metal and combines with oxygen in air to form layer of magnesium oxide on its surface. This oxide protects magnesium from burning. Therefore, it is should be cleaned with sandpaper before burning in air.

Q8. What do you mean by double displacement reactions? Give one example (chemical equation).

Ans – In this type of reaction two elements displaces each other from their respective solutions.

Example – Na2SO4 + BaCl2 → Ba SO4 + 2NaCl

Q9. What is a balanced chemical equation? Why should chemical equations be balanced?

Ans – In a balanced chemical equations the number of atoms in each side either in reactant or product must be equal. This equality of atoms in chemical equations  is called balanced chemical equations.

The chemical equation needs to be balanced so that it follows the law of conservation of mass.

Q10. Which reactant is Oxidised in the following chemical reaction?

CuO + H2 → Cu + H2O

Ans – Hydrogen is oxidised.

Q11. Which of the following reactant is reduced in chemical reaction?

Cuo + H2 → Cu + H2O

Ans – Copper oxide is reduced as it loses oxygen.

Q12. What is redox reaction ? Give an example.

Ans – A reaction in which one reactant gets oxidised is called oxidation reaction and a reaction in which one reactant gets reduced is called Reduction Reaction. When both of them combined is called Oxidation-Reduction reactions or redox reactions.

Example – CuO + H2 → Cu + H2O . In this example copper oxide is losing oxygen and is reduced. The hydrogen is gaining oxygen and is being oxidised.

HBSE Class 10 Science Chapter 2 – Acid, Bases and Salt Important Questions 2024-25

Q1. What happens when gypsum is heated to 373 K ? Give chemical equation for it.

Ans – On heating gypsum at 373 K, it loses water molecules and becomes calcium sulphate hemihydrate (CaSO4.½H2O). This is called Plaster of Paris, the substance which doctors use as plaster for supporting fractured bones in the right position.

ΔCaSO4.2H2O → CaSO4.½H2O + (3/2)H2O

Q2. What is chlor-alkali process? Explain with the help of a chemical equation.  Most Important

Ans – When electricity is passed through an aqueous solution of sodium chloride (called brine), it decomposes to form sodium hydroxide. The process is called the chlor-alkali process because of the products formed– chlor for chlorine and alkali for sodium hydroxide.

2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2 (g) + H2 (g)

Chlorine gas is given off at the anode, and hydrogen gas at the cathode. Sodium hydroxide solution is formed near the cathode. The three products produced in this process are all useful.

Q3. What is neutralisation reaction ? Give one example. Most Important

Ans – The reaction between an acid and a base to give a salt and water is known as a neutralisation reaction.

Base + Acid → Salt + Water

Example – NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Q4. Write common name and two uses of NaHCO3.

Ans – Common name of NaHCO3 is baking soda.

Two uses of Baking soda are as :
(i) For making baking powder.
(ii) Used in soda-acid fire extinguishers.
(iii) Used as ingredient in antacids.

Q5. What is chemical formula of baking soda? Give chemical equation used in its preparation. Most Important

Ans – Chemical formula of baking soda is NaHCO3 .

Chemical equation : NaCl + H2O + CO2 + NH3 → NH4Cl + NaHCO3

Q6. What is the chemical formula of washing soda ? Give chemical equation used in its preparation.

Ans – Chemical formula of washing soda is Na2CO3.10H2O

Chemical equation : Na2CO3 + 10H2O → Na2CO3.10H2O

Q7. Give two important uses of washing soda and baking soda.

Ans – Two uses of Baking soda are as :
(i) For making baking powder.
(ii) Used in soda-acid fire extinguishers.
(iii) Used as ingredient in antacids.

Two important uses of washing soda are as :
(i) Washing soda is used in glass, soap and paper industries.
(ii) Used for removing permanent hardness of water.
(iii) Used in manufacture of sodium compounds such as borax.

Q8. Why do acids not show acidic behaviour in the absence of water?

Ans – Because in the absence of water, acids do not dissociate to produce H + ions. It is only in the presence of water, that acids dissociate and produce H + ions, which are responsible for the acidic behaviour of acids. Hence acids will not exhibit acidic behaviour in the absence of water.

Q9. Four solution A, B, C and D when tested with a universal indicator, showed pH as 1, 7, 6 and 13 respectively Which solution is neutral, strongly alkaline, weak alkaline or weak acid and strongly acidic ? Most Important

Ans – pH of neutral solution = 7

pH of strongly alkaline = 13

pH of weak alkaline or weak acid = 6

pH of strongly acidic = 1

HBSE Class 10 Science Chapter 3 – Metals and Non-Metals Important Questions 2024-25

Q1. Explain reactivity series with examples. Most Important

Ans – The reactivity series is a list of metals arranged in the order of their decreasing reactivity.

Q2. What are amphoteric oxides ? Give two examples of amphoteric oxides. Most Important

Ans – Metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides.

Example – Aluminium oxide (Al2O3), zinc oxide (ZnO)

Q3. Write brief note on Electrolytic Refining. Most Important

Ans – Many metals, such as copper, zinc, tin, nickel, silver, gold, etc., are refined electrolytically is known as Electrolytic Refining. In this process, the impure metal is made the anode and a thin strip of pure metal is made the cathode. A solution of the metal salt is used as an electrolyte. On passing the current through the electrolyte, the pure metal from the anode dissolves into the electrolyte. An equivalent amount of pure metal from the electrolyte is deposited on the cathode. The soluble impurities go into the solution, whereas, the insoluble impurities settle down at the bottom of the anode and are known as anode mud.

Q4. In which state ionic compound exists? Why do they have high melting point ? Most Important
OR
Why do ionic compounds have high meltingpoints ?

Ans – Ionic compounds are solid in physical state. Ionic compounds have high melting point because a large amount of energy is required to break the strong inter-ionic attraction.

Q5. Write electronic configuration of Aluminium (At. No. – 13 ) and Sulphur (At. No. – 16).

Ans – Electronic Configuration of Aluminium = 2, 8, 3

Electronic configuration of Sulphur = 2, 8, 6

Q6. Why is sodium kept in kerosene oil?

Ans – Sodium is highly reactive metal. If it is kept in open it can react with oxygen to catch fire. So, sodium is kept in kerosene to prevent its reaction with oxygen.

Q7. Differentiate between Alloy and Amalgam.

Ans.

Alloy Amalgam
An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.

Example – Bronze, Brass etc.

 An alloy is a homogeneous mixture of a metal in mercury.

Example – zinc-mercury, sodium-mercury etc.

Q8. What is thermit reaction? Give chemical equation for it. Most Important

Ans – The reaction of iron oxide (Fe2O3) with aluminium is used to join railway tracks or cracked machine parts. This reaction is known as the thermit reaction.
Fe2O3 (s) + 2Al(s) → 2Fe(l) + Al2O3 (s) + Heat

Q9. Explain the following in context of metals :
(i) Malleability
(ii) Ductility
(iii) Conductor of heat and electricity
(iv) Sonorous

Ans – (i) Malleability : The ability of metals to drawn into thin sheets is called malleability.

(ii) Ductility : The ability of metals to drawn into thin wires is called ductility.

(iii) Conductor of heat and electricity : Metals are good conductor of heat and electricity.

(iv) Sonorous : It is a property of metal in which metals produce a sound on striking a hard surface.

Q10. Differentiate between Calcination and Roasting.

Ans – Calcination : The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination.

ZnCO3 (s) \displaystyle \xrightarrow{{Heat}} ZnO(s) + CO2 (g)

Roasting : The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting.

2ZnS(s) + 3O2 (g) \displaystyle \xrightarrow{{Heat}} 2ZnO(s) + 2SO2 (g)

Q11. What happens when metals are burnt in air ? Give one example.

Ans – Metals combine with oxygen to from metal oxides.

Metal + Oxygen → Metal oxide

Example – 2Cu + O2  →  2CuO

In this reaction, copper reacted with oxygen to form copper oxide.

Q12. What happens when metals react with acids ? Give one example.

Ans – Metals react with acids to give a salt and hydrogen gas.

Metal + Dilute acid → Salt + Hydrogen

Example – Mg + 2HCl  →  MgCl2 + H2 

In this reaction, magnesium reacted with hydrochloric acid to give magnesium chloride and hydrogen gas.

Q13. What happens when metals react with water ? Give one example.

Ans – Metals react with water and produce a metal oxide and hydrogen gas.

Metal + Water → Metal oxide + Hydrogen

Example –  2K(s) + 2H2O(l)  →  2KOH(aq) + H2 (g) + heat energy

Above example is a reaction of Potassium(metal) with water.

Q14. Differentiate between metal and non-metal on the basis of their chemical properties.

Ans.

Metals Non-Metal
1. Metals react with oxygen to form metal oxide. These oxides are basic in nature.

2.  Metals are electropositive, lose electrons and become a positive ion.

3. Metals are reducing agents.

 1. Non-metal react with oxygen to form non-metallic oxide. These oxides are acidic in nature.

2. Non-metals are electronegative, gain electrons and become negative ions.

3. Non-metals are oxidising agents.

Q15. Write a short note on electrolytic refining of Copper.

Ans – Electrolytic Refining of Copper : In this process, electrolyte is a solution of acidified copper sulphate. The anode is made up of impure copper , whereas, the cathode is a strip of pure copper. On passing electric current, pure copper from the anode dissolves into electrolyte. An equivalent amount of pure copper from the electrolyte is deposited on the cathode. The soluble impurities go into the solution, whereas, the insoluble impurities settle down at the bottom of the anode. Thus, copper is deposited on the cathode.

HBSE Class 10 Science Chapter 4 – Carbon and its Compound Important Questions 2024-25

Q1. Explain the following processes with help of chemical reactions:  Most Important
(a) Esterification
(b) Saponification
(c) Hydrogenation

Ans – (i) Esterification reaction: Esters are most commonly formed by reaction of an acid and an alcohol. Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester.

Generally esters are sweet smelling used in making perfumes and as flavouring agents.

(ii) Saponification : On treating with sodium hydroxide, which is an alkali, the ester is converted back to alcohol and sodium salt of carboxylic acid. This reaction is known as saponification.

CH3COOC2H5 \displaystyle \xrightarrow{{NaOH}} C2H5OH + CH3COONa

(iii) Hydrogenation : Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This reaction is commonly used in the hydrogenation of vegetable oils.

Q2. Explain in detail the Nomenclature of carbon compounds. Most Important

Ans – Nomenclature of carbon compounds can be done by the following method –

(i) Identify the number of carbon atoms in the compound. For example compound having one carbon uses prefix “meth”. A table for such prefix is given as :

Number of Carbon atoms  Prefix

1

2

3

4

5

6

7

8

9

10

Meth

Eth

Prop

But

Pent

Hex

Hept

Oct

Non

Dec

(ii) In case a functional group is present, it is indicated in the name of the compounds with either a prefix or a suffix .

(iii) If the name of the functional group is to be given as a suffix, and the suffix of the functional group begins with a vowel a, e, i, o, u, then the name of the carbon chain is modified by deleting the final ‘e’ and adding the appropriate suffix. For example, a three-carbon chain with a ketone group would be named in the following manner – Propane – ‘e’ = propan + ‘one’ = propanone.

(iv) Carbon compounds with single bond use ‘ane’ as suffix, whereas carbon compounds with double bond use ‘ene’ and with triple bond use ‘yne’.

Formulas : Alkanes (CnH2n+2) , Alkenes (CnH2n), Alkynes (CnH2n-2).

Q3. What happens when ethanol reacts with the following: Most Important
(a) Acidified potassium dichromate
(b) Sodium
(c) Hot. Conc. H2SO4

Ans –

(a) 

Alkaline potassium permanganate or acidified potassium dichromate are oxidising alcohols to acids, that is, adding oxygen to the starting material.

(b) 2Na + 2CH3CH2OH → 2CH3CH2O–Na+ + H2

When ethanol react with sodium then sodium ethoxide and hydrogen gas is the product.

(c) 

When ethanol react with hot concentrated sulphuric acid than sulphuric acid can be regarded as dehydrating agent which removes water from ethanol.

Q4. Explain the mechanism of cleaning action of soaps. Most Important

Ans – The dirt present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in the water. The dust particles are then easily rinsed away by water.

Q5. Give two differences between soaps and detergents.

Ans.

Soaps Detergents
Molecules of soap are sodium or potassium salts of long-chain carboxylic acids. Molecules of detergents are sodium salts of sulphonic acids or ammonium salts with chlorides and bromides ions.
Soaps are useful in soft water only. Detergents are useful in both soft water and hard water.

Q6. Draw the structures of all possible isomers of pentane. Most Important
OR
Draw all the structural isomers of pentane (C5H12).

Ans –

Q7. Explain with examples the following properties of carbon compounds: Most Important
(a) Oxidation Reaction
(b) Addition Reaction
(c) Substitution Reaction

Ans –

(a) Carbon compounds can be easily oxidised on combustion. In addition to this complete oxidation, we have reactions in which alcohols are converted to carboxylic acids –

(b) Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This reaction is commonly used in the hydrogenation of vegetable oils using a nickel catalyst. Vegetable oils generally have long unsaturated carbon chains while animal fats have saturated carbon chains.

(c) Saturated hydrocarbons are fairly unreactive and are inert in the presence of most reagents. However, in the presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one. It is called a substitution reaction because one type of atom or a group of atoms takes the place of another. A number of products are usually formed with the higher homologues of alkanes.

CH4 + Cl2 → CH3Cl + HCl (in the presence of sunlight)

Q8. Give chemical equation for the reaction of ethanoic acid with following: Most Important
(a) NaOH
(b) Na2CO3
(c) NaHCO3
(d) CH3CH2OH in the presence of acid

Ans –

(a) CH3COOH + NaOH → CH3COONa + H2O

(b) 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2

(c) CH3COOH + NaHCO3 → CH3COONa + H2O + CO2

(d)

Q9. Write the names of the following compounds :  Most Important

  4.  CH3-CL
  5.  CH3-CH2-CH2-OH
  6. CH3 – CH2 – Cl
  7. CH3 – CH2 – OH
  8.  CH3 – CH2 -CHO
  9. CH3-CH2-CH2– Br
  10.  CH3-C≡CH
  11. CH3-OH
  12.  CH3-CH=CH2
  13. CH3-CH2-Br
     
  14. CH3COOH
  15. CH3Br
  16. CH3COCH3
  17. CH3CHO
  18. CH3-CH2-COOH
  19. CH3-CH2-CH2-CH3

Ans –

  1. Ethanoic acid
  2. Propanoic acid
  3. Ethyl acetate
  4. methyl chloride
  5. propan-1-ol
  6. chloroethane
  7. ethanol
  8. propanal
  9. 1-bromobutane
  10. propyne
  11. methanol
  12. propene
  13. bromoethane
  14. ethanoic acid
  15. methyl bromide
  16. acetone
  17. acetaldehyde
  18. propanoic acid
  19. butane
  20. propionic acid
  21. butanal
  22. acetaldehyde

Q10. What is hydrogenation? What is its industrial application?

Ans – Conversion of unsaturated hydrocarbon into saturated hydrocarbon by the addition of hydrogen in the presence of Nickel or palladium as catalyst is known as hydrogentation.

Industrial Application –

This process is used for conversion of vegetable oil into vegetable ghee.

vegetable oil + H2 \displaystyle \xrightarrow{{\text{Ni, 473k}}} Vegetable Ghee

Vegetable oils have double carbonic bond. When hydrogen gas is made to pass through these in the presence of Nickel action as catalyst at 473k, it converts into solid fat.

Q11. Which of the following hydrocarbons undergo addition reaction?

C2H6, C3H8, C3H6, C2H2

Ans – Only unsaturated hydrocarbon undergo addition reaction. So C3H8 and C2H2 will undergo addition reaction.

Q12. Define homologous series and functional group. Most Important 

Ans –

Homologous series – Such a series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series.

Functional Group – The element replacing hydrogen is referred to as a heteroatom. These heteroatoms and the group containing these confer specific properties to the compound, regardless of the length and nature of the carbon chain and hence are called functional groups.

Q13. What are saturated and unsaturated hydro-carbons? Most Important 

Ans –

  • Saturated Hydrocarbons: Those hydrocarbons which contain only single bonds between carbon atoms. Examples include alkanes.
  • Unsaturated Hydrocarbons: Those hydrocarbons which contain at least one double or triple bond between carbon atoms. Examples include alkenes and alkynes.

Q14. Explain two properties of carbon atom which lead to the huge number of carbon compounds.

Ans –

  1. Catenation – The carbon atoms have an astonishing property to combine and form bond with other carbon atoms to form long chain compounds. This property is known as catenation. In this, either long chain of carbon are in ring form or the carbon atoms join in single, double or triple bond.
  2. Tetravalency – Carbon has four electrons in the outermost shell. This is why its valency is four and it has got capacity to make bonds with other elements. Oxygen, Hydrogen, Nitrogen, Sulphur, Chlorine and many other elements can make new compounds with the help of carbon.

Q15. Write the formula of benzene and draw its structure. Most Important

Ans – Formula of benzene – C6H6

Q16. Differentiate between Hard water and Soft water.

Ans –

Characteristic Hard Water Soft Water
Mineral Content High concentration of calcium and magnesium ions Low concentration of calcium and magnesium ions
Scale Formation Forms scale or deposits when heated Does not form scale when heated
Lathering Does not lather well with soap Lathers well with soap
Effect on Appliances Mineral deposits can accumulate, reducing efficiency and lifespan Less likely to cause mineral buildup, promoting longevity and efficiency
Common Ions Present Calcium (Ca²⁺), magnesium (Mg²⁺), often in the form of bicarbonates, sulfates, or chlorides May contain higher concentrations of sodium (Na⁺) or potassium (K⁺), depending on the softening process used

Q17. Why are carbon and its compound used as fuels for most applications ? Most Important

Ans – When carbon and its compounds are made to burn in the presence of excess of air or oxygen large amount of heat, energy and light are produced. They result in continuous combustion. They do not require large amount of heat energy. These do not produce smoke or poisonous gases. No residue is left after their burning and has high calorific value. These are convenient to use as a fuel and except coal these do not leave any residence.

Q18. Draw structure of Cyclohexane.

Ans – 

Q19. What do you mean by structural isomers ? Give one example.

Ans – The compounds with identical molecular formula but different structures are called structural isomers.

Example – Pentane have formula C5H12 can be represented as

Q20. Explain alkane, alkene and alkyne with suitable example.

Ans – Alkane : All these carbon compounds which contain only carbon and hydrogen are called hydrocarbons. Among these, the saturated hydrocarbons are called alkanes. Example – Methane, Ethane, Propane etc.

Alkene : The unsaturated hydrocarbons which contain one or more double bonds are called alkenes. Example – Ethene, Propene, Butene etc.

Alkyne : The unsaturated hydrocarbons which contain one or more triple bonds are called alkynes. Example – Ethyne, propyne, butyne etc.

Q21. Complete the following chemical reactions :

(i) CH3-CH2-OH + O2 \displaystyle \to

(ii) CH3CH2OH \displaystyle \xrightarrow{{Alkaline-KMn{{O}_{4}}hot}}

(iii) CH3COOC2H5 \displaystyle \xrightarrow{{NaOH}}

(iv) CH3COOH + NaHCO3 \displaystyle \to

(v) Na + C2H5OH \displaystyle \to

(vi) C2H5OH \displaystyle \xrightarrow{{\text{Hot Conc}\text{. H2SO4}}}

Ans –

(i) CH3-CH2-OH + O2 \displaystyle \to CH3-CO2-H(l) + H2O(l)

(ii) CH3CH2OH \displaystyle \xrightarrow{{Alkaline-KMn{{O}_{4}}hot}} CH3COOH

(iii) CH3COOC2H5 \displaystyle \xrightarrow{{NaOH}} CH3​COONa+C2​H5​OH

(iv) CH3COOH + NaHCO3 \displaystyle \to CH3​COONa+H2​O+CO2​

(v) 2Na + 2C2H5OH \displaystyle \to 2C2​H5​ONa+H2​

(vi) C2H5OH \displaystyle \xrightarrow{{\text{Hot Conc}\text{. H2SO4}}} C2​H4​ + H2​O

HBSE Class 10 Science Biology Portion Important Questions 2024-25

HBSE Class 10 Science Chapter 5 – Life Processes Important Questions 2024-25

Q1. Describe the excretion in plants. Most Important

Ans – Plants use completely different strategies for excretion than those of animals. Oxygen itself can be thought of as a waste product generated during photosynthesis. They can get rid of excess water by transpiration. For other wastes, plants use the fact that many of their tissues consist of dead cells, and that they can even lose some parts such as leaves. Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off. Other waste products are stored as resins and gums, especially in old xylem. Plants also excrete some waste substances into the soil around them.

Q2. Describe the respiratory system of human beings. Most Important
OR
Explain the structure of human respiratory system with the help of well labelled diagram.

Ans – The respiratory system in humans is a complex network of organs and structures that work together to facilitate the exchange of gases, primarily oxygen and carbon dioxide, between the body and the external environment. The main components of the respiratory system include the respiratory tract and the lungs.

Components of the Respiratory System:

  1. Nasal Cavity:
    • The respiratory process begins in the nasal cavity, where air is filtered, moistened, and warmed as it enters the respiratory system.
  2. Trachea (Windpipe):
    • The trachea is a tube composed of cartilage rings that extends from the larynx to the bronchi. It provides a rigid structure to maintain an open airway.
  3. Bronchi and Bronchioles:
    • The trachea branches into two bronchi, one entering each lung. Bronchi further divide into smaller bronchioles, which lead to the alveoli. They conduct air into the lungs.
  4. Lungs:
    • The lungs are paired, spongy organs responsible for gas exchange. The right lung has three lobes, while the left lung has two lobes to accommodate the heart. Each lung is surrounded by a pleural membrane.
  5. Alveoli:
    • Alveoli are tiny, air-filled sacs located at the end of bronchioles. They are the site of gas exchange, where oxygen from inhaled air diffuses into the bloodstream, and carbon dioxide is released from the bloodstream into the air.

The respiratory system plays a vital role in providing the body with the oxygen necessary for cellular respiration and removing carbon dioxide, a waste product of metabolism.

Q3. Describe the structure of nephron and how is urine produced? Most Important
OR
Describe structure and functioning of nephron. Most Important

Ans – 

The basic filtration unit in the kidneys is a cluster of very thin-walled blood capillaries. Each capillary cluster in the kidney is associated with the cup-shaped end of a coiled tube called Bowman’s capsule that collects the filtrate. Each kidney has large numbers of these filtration units called nephrons packed close together.

Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube. The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra. The bladder is muscular, so it is under nervous control. As a result, we can usually control the urge to urinate.

Q4. Draw a well labelled diagram of excretory system and explain the process of urine formation in human being.
OR
Explain the structure of human excretory system with the help of a well labelled diagram.

Ans –

Process of urine formation in human being –

The excretory system of human beings includes a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Each kidney has large numbers of these filtration units called nephrons packed close together. Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube. The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra. The bladder is muscular, so it is under nervous control. As a result, we can usually control the urge to urinate.

Q5. What is lymph ? How is it transported ? What are its functions ? Most Important

Ans – There is another type of fluid also involved in transportation. This is called lymph or tissue fluid. Through the pores present in the walls of capillaries some amount of plasma, proteins and blood cells escape into intercellular spaces in the tissues to form the tissue fluid or lymph. It is similar to the plasma of blood but colourless and contains less protein. Lymph drains into lymphatic capillaries from the intercellular spaces, which join to form large lymph vessels that finally open into larger veins. Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood.

Q6. What is transpiration? How does it take place? What is its role?

Ans – Transpiration : The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.

Transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves. It also helps in temperature regulation. The effect of root pressure in transport of water is more important at night. During the day when the stomata are open, the transpiration pull becomes the major driving force in the movement of water in the xylem.

Q7. Describe structure and functioning of human heart. Most Important

Ans –

The heart is a muscular organ which is as big as our fist. Because both oxygen and carbon dioxide have to be transported by the blood, the heart has different chambers to prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide. The carbon dioxide-rich blood has to reach the lungs for the carbon dioxide to be removed, and the oxygenated blood from the lungs has to be brought back to the heart. This oxygen-rich blood is then pumped to the rest of the body.
Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, relaxes, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body. De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it relaxes. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation. Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do. Valves ensure that blood does not flow backwards when the atria or ventricles contract.

Q8. Draw a well labelled diagram of cross-section of leaf. Most Important

Ans –

Q9. Draw a well labelled diagram of human digestive system.

Ans – 

Q10. What are the differences between aerobic and anaerobic respiration? Most Important

Ans –

Aerobic Respiration Anaerobic Respiration
It occurs in the presence of O2. It occurs in the absence of O2.
It occurs in cytoplasm and mitochondria. It occurs only in cytoplasm.
Carbohydrate (glucose) is oxidized completely using molecular oxygen. Carbohydrate (glucose) is incompletely oxidized. Molecular oxygen is not used.
CO2 and water are the end products. Lactic acid or ethanol and CO2 are the end products.

Q11. What are the differences between transport of Materials in xylem and phloem?

Ans –

Xylem Phloem
Xylem transports water and minerals from roots to the leaves and other plant parts. Phloem transports prepared food (sugars and amino acids) from the leaves to the other parts of the plant body and to the storage organs.
Conducting elements are tracheids and vessels, which are dead elements. Conducting elements of phloem are sieve tubes, which are living cells.
There is only upward conduction of water and dissolved minerals. There is two way transport (translocation) of dissolved food through the phloem.

Q12. What is photosynthesis? Write various events which take place during this process. Most Important

Ans –

Photosynthesis:

Photosynthesis is the process by which green plants, algae, and some bacteria use sunlight to convert carbon dioxide and water into glucose (a type of sugar) and oxygen. This process takes place in the chloroplasts of plant cells.

The overall equation for photosynthesis is :

6CO2+6H2O+light energy → C6H12O6 + 6O2

Events During Photosynthesis:

  1. Light Absorption:
    • Chlorophyll, a green pigment in chloroplasts, absorbs sunlight.
  2. Water Uptake (Photolysis):
    • Plants absorb water from the soil, and in the presence of sunlight, water molecules are split into oxygen, protons, and electrons.
  3. Formation of ATP :
    • The energy from sunlight is used to convert ADP (adenosine diphosphate) and inorganic phosphate into ATP (adenosine triphosphate).
  4. Carbon Dioxide Fixation :
    • Carbon dioxide from the air is fixed into a stable organic compound .
  5. Glucose Formation:
    • The organic compounds glucose is formed, serve as an energy source for the plant.
  6. Oxygen Release:
    • Oxygen is released as a byproduct into the atmosphere during the light-dependent reactions.

Q13. What is the role of saliva in the digestion of food?

Ans – Saliva contains a digestive enzyme called salivary amylase, which breaks down starch into sugar. Saliva has many functions in the digestion process as follows:

  1. It is used to lubricate the mouth.
  2. It helps to swallow the food.
  3. It helps to protect the teeth from bacterial infections.
  4. It aids in the food digestion.

HBSE Class 10 Science Chapter 6 – Control and Coordination Important Questions 2024-25

Q1. What is geotropism ? Give an example. Most Important

Ans – It is type of movement of plants in which the roots of a plant always grow downwards while the shoots usually grow upwards and away from the earth. example – downwards movement of roots.

Q2. Draw a well labelled diagram of a neuron. Most Important

Ans – 

Q3. What happens at synapse between two neurons? Most Important

Ans – A synapse allows delivery of electrical impulses from neurons to other cells, such as muscles or gland.

Q4. Draw a well labelled diagram of Reflex arch.

Ans – 

Q5. What is the role of the brain in reflex action ?

Ans – The brain and spinal cord constitute the central nervous system. They receive information from all parts of the body and integrate it. The brain thus allows us to think and take actions based on that thinking. As you will expect, this is accomplished through a complex design, with different parts of the brain responsible for integrating different inputs and outputs. The brain has three such major parts or regions, namely the fore-brain, mid-brain and hind-brain.

Q6. Write down the functions of cerebellum and medulla. Most Important

Ans –

Cerebellum Medulla
Controls voluntary actions Controls involuntary actions
Actions like walking in a straight line, riding bicycle or picking up a pencil etc. Actions including blood pressure, salivation and vomiting

Q7. Why is the use of iodised salt advisable ? Write the functions of the hormone secreted by thyroid gland.

Ans – Iodine is necessary for the thyroid gland to make thyroxin hormone which regulates carbohydrate, protein and fat.

Q8. What are the functions of forebrain?

Ans – The fore-brain is the main thinking part of the brain. Separate areas of the fore-brain are specilised for hearing, smell and sight.

Q9. Iodine is necessary for the synthesis of which hormone? Most Important

Ans – Thyroxin.

Q10. Explain the process of response to touch in sensitive plant.

Ans – Leaves of the sensitive plant protect themselves from predators and environmental conditions by folding in response to touch. When we touch the leaves of these plants, they begin to fold up and droop.

Q11. How are brain and spinal cord protected in human body?

Ans – Our body is designed in such a way that the the brain sits inside a bony box. Inside the box, the brain is contained in a fluid-filled which provides further shock absorption. Spinal cord is protected by vertebral column or backbone which is a hard, bumpy structure.

Q12. Which gland secrete the growth hormone? What happens due to deficiency and excess of this hormone?

Ans – Pituitary gland secrete the growth hormone.

Deficiency of growth hormone leads to dwarfism, whereas, excess of growth hormone leads to gigantism/extremely tall.

HBSE Class 10 Science Chapter 7 – How do Organisms Reproduce Important Questions 2024-25

Q1. Describe the process of budding in Hydra. Most Important

Ans – Hydra use regenerative cells for reproduction in the process of budding. In Hydra, a bud develops as an outgrowth due to repeated cell division at one specific site . These buds develop into tiny individuals and when fully mature, detach from the parent body and become new independent individuals.

Q2. Draw a well labelled diagram of Longitudinal section of a flower. Most Important

Ans –

Q3. Draw a well labelled diagram of human female reproductive system.
OR
Explain human female reproductive system with diagram.

Ans –  The female germ-cells or eggs are made in the ovaries. They are also responsible for the production of some hormones. On reaching puberty, one egg is produced every month by one of the ovaries. The egg is carried from the ovary to the womb through a thin oviduct or fallopian tube. The two oviducts unite into an elastic bag-like structure known as the uterus.

Q4. What happens when the egg is not fertilized?
OR
Why does menstruation occur?

Ans – If the egg is not fertilised, it lives for about one day. Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilised egg. Thus its lining becomes thick and spongy. This would be required for nourishing the embryo if fertilisation had taken place. Now, however, this lining is not needed any longer. So, the lining slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstruation. It usually lasts for about two to eight days

Q5. Discuss the structure of female reproductive part of a flower.

Ans – Pistil is present in the centre of a flower and is the female reproductive part. It is made of three parts. The swollen bottom part is the ovary, middle elongated part is the style and the terminal part which may be sticky is the stigma. The ovary contains ovules and each ovule has an egg cell. The male germ-cell produced by pollen grain fuses with the female gamete present in the ovule. This fusion of the germ-cells or fertilisation gives us the zygote which is capable of growing into a new plant.

Q6. How is the process of pollination different from fertilization? Most Important

Ans – 

Pollination Fertilization
  1. The process of transfer of pollen grains from the anther to stigma is known as pollination.
  2. It takes place on the stigma of either the same flower or different flower.
  3. External agents like wind, insects etc. are required.
  4. It is a physical process .
  5. It occurs only in seeds .
  1. Fertilization is the fusion of male and female gametes to form zygote.
  2. It takes place inside an ovule.
  3. No external agent is required.
  4. It is a biological process .
  5. It occurs in both plants and animals of various types.

Q7. Describe three different methods of contraception.

Ans – Contraception to avoid pregnancy can be achieved by the use of condoms, oral pills, copper-T and other methods.

Q8. Write those changes of puberty that are common to girls and boys.

Ans – 

Changes Girls during Puberty Boys during Puberty
Growth Significant increase in height. Significant increase in height.
Secondary Sexual Characteristics Development of breasts, widening of hips, onset of menstruation. Growth of facial and body hair, deepening of voice.
Hormonal Changes Increase in estrogen levels. Increase in testosterone levels.
Body Hair Growth Growth of pubic hair and underarm hair. Growth of pubic hair, facial hair, and body hair.
Skin Changes Changes in skin texture and oiliness. Changes in skin texture and oiliness.

Q9. What is difference between binary fission and multiple fission ? Explain with example.

Ans –

Feature Binary Fission Multiple Fission
Number of Offspring Two (2) Multiple
Genetic Identity Offspring are genetically identical to the parent Offspring may not be genetically identical
Process Single parent cell divides into two equal halves Single parent cell produces multiple offspring
Examples Bacteria, Amoeba Plasmodium (malaria parasite)

Q10. What are different contraceptive methods? How are they important for reproductive health? Most Important

Ans – Contraceptive methods to avoid pregnancy can be achieved by the use of condoms, oral pills, copper-T and other methods. It’s important to note that the choice of contraceptive method depends on individual preferences, health considerations, and lifestyle factors.

HBSE Class 10 Science Chapter 8 – Heredity Important Questions 2024-25

Q1. How do Mendel’s experiment show that traits are inherited independently? Most Important

Ans – In a dihybrid cross, Mendel observed that when two pairs of traits or characters were considered, each trait expressed independent of the other. Mendel crossed pure breeding tall plants having round seeds with pure breeding short plants having wrinkled seeds. The plants of F1 Generation were all tall with round seeds indicating that the traits of tallness and round seeds were dominant. Self breeding of F1 yielded plants with characters of 9 tall round seeded, 3 tall wrinkled seeded, 3 short round seeded and 1 short wrinkled seeded. Tall wrinkled seeded and short round seeded plants are new combinations which can develop only when the traits are inherited independently.

Q2. How do Mendel’s experiments show that traits may be dominant or recessive ?

Ans – Mendel studied several contrasting characters of pea plants. He found that reproduction by cross pollination of plants with alternative traits resulted in the first generation F1 displaying only one trait and no other trait. For example, when Mendel hybridized the tall pea plant and the short plant, he received all the plants tall in the first offspring generation F1. This meant that only one ancestral trait of the two traits showed. There was no mixed evidence of both of them. He grew F1 generation plants by self pollination. Not all plants in this second generation F2 were tall. A quarter of the plants were dwarfs. Mendel called the trait of tall plants dominant and the trait of dwarf plants recessive.

Q3. How is the sex of the child determined in human beings? Most Important

Ans – In human beings, sex is determined on the basis of specific sex chromosomes. Males have XY chromosomes and females have XX chromosomes. It is clear from this that the female does not have the Y chromosome. When offspring are produced by male-female combination, the female may not be able to produce a male infant at any stage because the male infant must have XY chromosomes.

In fertilization, if the X chromosome of a man is fused with the X chromosome of the woman, then it will form an XX pair. Hence, the child will be in the form of a girl.

But when a man’s Y chromosome combines with the female’s chromosome X, XY will be formed. This will lead to the birth of a boy.

Q4. As per Mendel’s Law, describe the independent assortment of two separate traits (rounded and green seeds) with ( wrinkled and yellow seeds) along with diagram.

Ans – Mendel’s Law of Independent Assortment states that the alleles for different traits segregate independently of each other during the formation of gametes. Let’s consider two traits: seed shape (rounded or wrinkled) and seed color (green or yellow).

In this case, let’s represent the dominant alleles for each trait with capital letters (R for round seeds, Y for yellow seeds) and the recessive alleles with lowercase letters (r for wrinkled seeds, y for green seeds).

If an individual has the genotype RrYy (heterozygous for both traits), the possible gametes produced during the process of independent assortment would be:

  1. RY
  2. Ry
  3. rY
  4. ry

These combinations result from the independent assortment of alleles for seed shape (R and r) and seed color (Y and y). Each gamete represents a unique combination of alleles.

Here’s a simplified diagram to illustrate the independent assortment:

This diagram shows the possible combinations of alleles for seed shape (R and r) along the horizontal axis and seed color (Y and y) along the vertical axis. The four squares represent the different combinations of alleles in the gametes due to the independent assortment of these traits.

Q5. Rounded seeds (dominant trait) were crossed with wrinkled seeds (recessive trait).
(i) What type of seeds will be produced in F1 generation ?
(ii) By self-pollination in F₁ seeds, what percentage of seeds will be rounded shape in F2 generation ?
Explain with diagram.

Ans – When rounded seeds (dominant trait, represented by the symbol R) are crossed with wrinkled seeds (recessive trait, represented by the symbol r), the F1 generation will be heterozygous for the trait, having the genotype Rr.

(i) F1 Generation: All the seeds in the F1 generation will have the rounded phenotype because the dominant trait (R) masks the expression of the recessive trait (r). Therefore, all seeds in the F1 generation will be rounded.

(ii) F2 Generation: When individuals from the F1 generation (Rr) are self-pollinated, the possible combinations of alleles in the F2 generation can be predicted as:

R r
R RR Rr
r Rr rr

In this table, the possible genotypes are RR, Rr, Rr, and rr.

  • The phenotypes corresponding to these genotypes are:
    • RR and Rr: Rounded seeds
    • rr: Wrinkled seeds

So, in the F2 generation, the phenotypic ratio will be 3:1 for rounded seeds to wrinkled seeds.

If you’re looking for the percentage of rounded seeds in the F2 generation, you would consider the RR and Rr genotypes together. In this case, since both genotypes express the rounded phenotype, the percentage of rounded seeds would be 75% (3 out of 4) in the F2 generation.

HBSE Class 10 Science Chapter 13 – Our Environment Important Questions 2024-25

Q1. Define ecosystem.

Ans – All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem. Thus, an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals.

Example : Forests, ponds, lakes, gardens, rivers etc.

Q2. “Flow of energy is unidirectional in ecosystem”, explain.

Ans – Flow of energy is unidirectional in ecosystem means the energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs. As it moves progressively through the various trophic levels it is no longer available to the previous level.

Q3. Write full form of UNEP. Most Important

Ans – United Nations Environment Programme

Q4. Name the solar radiation from which the surface of earth is shielded by ozone layer.

Ans – ultraviolet (UV) radiation

Q5. Which synthetic chemical is responsible for depletion of ozone layer?

Ans – chlorofluorocarbons (CFCs)

Q6. What are the advantages and disadvantages of ozone ?

Ans – Advantages of ozone : At higher levels of atmosphere, it protect the surface of earth from ultraviolet radiations. These radiations are highly damaging as they cause skin cancer in human skins.

Disadvantages of ozone : On ground level, It is a deadly poison.

Q7. Write full form of CFCs.

Ans – chlorofluorocarbons

HBSE Class 10 Science Physics Important Questions 2024-25

HBSE Class 10 Science Chapter 9 – Light : Reflection and Refraction Important Questions 2024-25

This Table is Most important for this chapter. Must revise this.

1. Nature, position and relative size of the image formed by a convex lens for various positions of the object

2. Image formation by a concave mirror for different positions of the object

Q1. Using a ray diagram, explain the position, relative size and nature of image of an object placed between the F1 and 2F1 of a convex lens.

Ans –

Here AB is the object. A’B’ is the Image of the object.

Position of object – Between F1 and 2F1

Position of the image – Beyond 2F2

Relative size of the image – Enlarged

Nature of the image – Real and inverted

Q2. What is power of a Lens ? Define one Dioptre (1D) power of a lens. Most Important

Ans – The degree of convergence or divergence of light rays achieved by a lens in expressed in terms of its power. The power of a lens is defined as the reciprocal of its focal length.

P = 1/f

Dioptre is the SI unit of power of a lens. 1 Diopte can be defined as the power of a lens of focal length 1 metre. Dioptre is denoted by D.

Q3. An object is placed at the centre of curvature (c) of a concave mirror. Draw the ray diagram to depict the position, size and the nature of image formed. Most Important

Ans –

Here AB is the object. A’B’ is the Image of the object.

Position of object – At Centre of curvature C

Position of the image – At Centre of curvature C

Relative size of the image – same size

Nature of the image of an object – Real and Inverted

Q4. An object is placed at a position in between the main focus (F1) and the optical centre (O) of a convex lens. Draw a ray diagram showing the position, size and nature of the image formed. Most Important

Ans –

Here AB is the object. A’B’ is the Image of the object.

Position of object – Between focus F1 and Optical Centre O

Position of the image – On the same side of the lens as the object

Relative size of the image – Enlarged

Nature of the image – Virtual and Erect

Q5. Draw ray diagram and write nature of image formed if an object is placed at:
a) Between F1 and 2F1 of a concave lens.
b) Between F1 and 2F1 of a convex lens.

Ans –

(a) If the object is placed at F1 and 2F1 of a concave lens then nature of image will be virtual and erect. Here AB is the object. A’B’ is the Image of the object.

(b) If the object is placed at F1 and 2F1 of a convex lens then nature of image will be Real and inverted. Here AB is the object. A’B’ is the Image of the object.

Q6. Find the focal length of a lens of power -2.0 D. What type of lens is this? Most Important

Ans –

Power of lens P = 1/f

-2.0 = 1/f

f = 1/(-2) = -0.5 m

Concave lens has negative focal length. Therefore, given lens is concave.

Q7. Find the focal length of a lens of power +2.0 D. What type of lens in this ? Most Important

Ans – Power of lens P = 1/f

2.0 = 1/f

f = 1/(2) = 0.5 m

Convex lens has positive focal length. Therefore, given lens is concave.

Q8. Find the focal length of a convex mirror whose radius of curvature is 32 cm. Most Important

Ans – Given R = 32 cm

Using, R = 2f

where R is radius of curvature and f is focal length.

32 = 2f

f = 16 cm

Q9. Write the laws of reflection of light.

Ans – Laws of Reflection :

(i) The angle of incidence is always equal to the angle of reflection, and
(ii) The incident ray, the normal to the mirror at the point of incidence and the reflected ray , all lie in the same plane.

Q10. What is refraction of light? Write the laws of refraction of of light. Most Important

Ans – When light travelling obliquely from one medium to another, the direction of propagation of light in the second medium changes. This phenomenon is known as refraction of light.

Law of Refraction of light : 

(i) The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plant.
(ii) The ratio of sine of angle of incidence to the sine of angle of refraction is constant, for the light of a given colour and for the given pair of media. This law is also called snell’s law.

\displaystyle \frac{{\sin i}}{{\sin r}}=constant, 0<i<90°

Q11. Write the lens formula.

Ans – \displaystyle \frac{1}{v}-\frac{1}{u}=\frac{1}{f}

Where, u is object distance, v is image distance and f is focal length .

Q12. Write the mirror formula. Most Important

Ans –

\displaystyle \frac{1}{v}+\frac{1}{u}=\frac{1}{f}

Where v is image distance, u is object distance and f is focal length.

HBSE Class 10 Science Chapter 10 – The Human Eye and The Colourful World Important Questions 2024-25

Q1. Explain why the planets do not twinkle. Most Important

Ans – The planets are much closer to the earth, and are thus as extended sources. If we consider a planet as a collection of a large number of point-sized sources of light, the total variation in the amount of light entering our eye from all individual point-sized sources will average out to zero, thereby nullifying the twinkling effect.

Q2. Why do stars twinkle?

Ans – The twinkling of a star is due to atmospheric refraction of starlight. As the stars are very far away, they behave as almost a point source of light. When the light coming from stars enters the earth’s atmosphere, it gets refracted at different levels because of the variation in the air density. The path of rays of light coming from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering the eye flickers. So, sometimes, the star appears brighter and at some other time, fainter. Thus, the stars twinkle.

Q3. The prism split the incident white light into a band of colours. Write these colours name in sequence.
OR
Write the name of colours in sequence found after splitting of white light passing through a glass prism.

Ans – Colours in sequence : Violet, Indigo, Blue, Green, Yellow, Orange and Red.

It can be remember using VIBGYOR.

Q4. Define the following:
(a) Scattering of light
(b) Atmospheric refraction

Ans – (a) When white light from sun enters the earth’s atmosphere, the light gets scattered i.e., the light spreads in all directions by the dust particles, free water molecules and the molecules of the gases present in the atmosphere. This phenomenon is called scattering of light. The blue colour of the sky, colour of water in deep sea, the reddening of the sun at sunrise and the sunset are some of the wonderful phenomena of Scattering of Light.

(b) Flickering of objects seen through a turbulent stream of hot air rising above a fire or a radiator is due to atmospheric refraction. The air just above the fire becomes hotter than the air further up. The hotter air is lighter (less dense) than the cooler air above it, and has a refractive index slightly less than that of the cooler air. Since the physical conditions of the refracting medium (air) are not stationary, the apparent position of the object, as seen through the hot air, fluctuates. This wavering is thus an effect of atmospheric refraction

HBSE Class 10 Science Chapter 11 – Electricity Important Questions 2024-25

Q1. An electric motor takes 4 A from a 220 V line. Find the power of the motor and energy consumed in 3 hours.

Ans – Given, V = 220 V, I = 4 A,

t = 3 hour = 3×60×60 sec = 10800 sec

Power of motor P = VI
= 220V × 4 A
= 880 watt.

Energy consumed by motor in 3 hours will be

E = P × t
= 880 × 10800 joule
= 9.504 × 106 j

Q2. Why are the coils of electric irons and toasters are made of an alloy rather than a pure metal ? Most Important

Ans – Because an alloy has a higher resistance than a pure metal. The alloys also do not melt easily at high temperature.

Q3. How can three resistors of resistances 2Ω, 3Ω and 6Ω be connected to give a total resistance of 1Ω ? Most Important

Ans – If we connect all three resistors in parallel, we get

\displaystyle \frac{1}{{{{R}_{e}}}}=\frac{1}{{{{R}_{1}}}}+\frac{1}{{{{R}_{2}}}}+\frac{1}{{{{R}_{3}}}}

\displaystyle \frac{1}{{{{R}_{e}}}}=\frac{1}{2}+\frac{1}{3}+\frac{1}{6}=\frac{{3+2+1}}{6}=\frac{6}{6}=1

Re = 1Ω

and we also need net resistance 1Ω

Therefore, we have to connect all given resistors in parallel.

Q4. An electric refrigerator of power 400 W is allowed to run 10 hrs. per day. What is the cost of energy to operate it for 30 days at Rs. 4.00 per kWh? Most Important

Ans – The total energy consumed by the refrigerator in 30 days would be

400 W × 8.0 hour/day × 30 days = 96000 Wh = 96 kWh

Thus, the cost of energy to operate the refrigerator for 30 days is

96 kwh × Rs. 3.00 per kWh = Rs. 288

Q5. What is resistance ? State its SI unit. On which factors does the resistance of a conductor depends ? Most Important

Ans – Resistance is a property that resists the flow of electrons in a conductor. It controls the magnitude of the current. The SI unit of resistance is ohm (Ω). The resistance of a conductor depends directly on its length, inversely on its area of cross-section, and also on the material of the conductor.

Q6. What do you mean by earthing? Why should electrical appliances be earthed ? Most Important
OR
What is the function of an earthwire? Why is it necessary to earth metallic appliances ?

Ans – A Wire consist of three wires, the third is the earth wire that has green insulation and this is connected to a metallic body deep inside earth. This process is called earthing.

It is used as a safety measure to ensure that any leakage of current to a metallic body does not give any severe shock to a user.

Q7. An electric bulb is connected to a 220 V generator. The current is 0.50 A. What is the power of the bulb?

Ans – Given V = 220V, I = 0.50 A

Using,  P = VI

P = 220 V × 0.50 A

P = 110 J/s = 110 W

HBSE Class 10 Science Chapter 12 – Magnetic Effect of Electric Current Important Questions 2024-25

Q1. Explain Right hand thumb rule. Most Important

Ans – A convenient way of finding the direction of magnetic field associated with a current-carrying conductor is given in Figure. Imagine that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field, as shown in Figure. This is known as the right-hand thumb rule.

Q2. Briefly explain the Fleming’s left hand rule.

Ans – The three directions can be illustrated through a simple rule, called Fleming’s left-hand rule. According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.

Q3. Write two properties of magnetic lines of force.

Ans – Properties of magnetic line of force are :
(i) Magnetic field lines emerge from the North Pole and merge into the South Pole.
(ii) Inside the magnet, the direction of the magnetic field is from its south pole to the north pole.
(iii) Magnetic field lines are closed curves.
(iv) Two magnetic field lines never intersect each other.

(do any two)

Q4. What is a Solenoid? Draw the magnetic lines of force around a current carrying solenoid. Also throw some light on the use of solenoid. Most Important

Ans – A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a solenoid.

Use of Solenoid : A strong magnetic field produced inside a solenoid can be used to magnetise a piece of magnetic material, like soft iron, when placed inside the coil.

Q5. Draw the magnetic lines of force around a bar magnet. Most Important

Ans –  Magnetic field lines emerge from the North Pole and merge into the South Pole. Inside the magnet, the direction of the magnetic field is from its south pole to the north pole.

Q6. What do you mean by electromagnetic induction? Explain the use of Fleming’s right hand rule in finding the direction of current induced in the conductor. Most Important

Ans – Electromagnetic induction is the generation of voltage in a conductor by a changing magnetic field. Fleming’s Right-Hand Rule helps determine the direction of induced current in a conductor undergoing electromagnetic induction. Point your thumb in the direction of motion or force (applied field), index finger in the direction of the magnetic field, and the middle finger gives the direction of the induced current.

Q7. Explain the magnetic field due to current through a straight conductor. Describe the rule to find the direction of such a magnetic field.

Ans – When an electric current flows through a straight conductor, it produces a circular magnetic field around the conductor. The magnetic field produced by a given current in the conductor decreases as the distance from it increases. it can be noticed that the concentric circles representing the magnetic field around a current-carrying straight wire become larger and larger as we move away from it. This magnetic field can be determined using Fleming’s right-hand rule.

Fleming’s Right-Hand Rule for a Straight Conductor:

  1. Thumb: Point your thumb in the direction of the conventional current (the direction of the flow of positive charges).
  2. Index Finger: Extend your index finger in the direction of the magnetic field.
  3. Middle Finger: Your middle finger, positioned perpendicular to the thumb and index finger, indicates the direction of the magnetic force acting on the conductor.

So, if you grasp the conductor with your right hand such that your thumb points in the direction of the current, the magnetic field lines will circulate around the conductor in the direction shown by your fingers.

Q8. What are the two safety measures commonly used in electric circuits and appliances? Explain their working.

Ans – The two safety measures are fuses and earthing commonly used in electric circuits and appliances.

  1. Fuses:
    • Working Principle: Melts when current exceeds a set limit, breaking the circuit.
    • Operation: Prevents excessive current flow, protecting devices and preventing fire hazards.
    • Usage: Common in household appliances and electrical panels.
  2. Earthing:
    • Working Principle: Send all the charge into earth / ground.
    • Operation: Responds to extra charge or short circuit.
    • Usage: Widely used in residential and industrial electrical systems for safety and convenience.

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