# Magnetic Effect of Electric Current Class 10 Science Chapter 12 Important Question Answer – NCERT

 Class 10th Subject Science (NCERT) Category Important Questions

## Magnetic Effect of Electric Current Class 10 Science Chapter 12 Important Question Answer

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. Describe the magnetic field due to current in a solenoid.

Ans – A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a solenoid. The pattern of the magnetic field lines around a current-carrying solenoid is
shown in image. one end of the solenoid behaves as a magnetic north pole, while the other behaves as the south pole. The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the 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. The magnet so formed is called an electromagnet.

Q5. 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.

Q6. Describe the magnetic field due to current through a circular loop.

Ans – We have so far observed the pattern of the magnetic field lines produced around a current-carrying straight wire. Suppose this straight wire is bent in the form of a circular loop and a current is passed through it. We know that the magnetic field produced by a current-carrying straight wire depends inversely on the distance from it. Similarly at every point of a current-carrying circular loop, the concentric circles representing the magnetic field around it would become larger and larger as we move away from the wire. By the time we reach at the centre of the circular loop, the arcs of these big circles would appear as straight lines. Every point on the wire carrying current would give rise to the magnetic field appearing as straight lines at the center of the loop. By applying the right hand rule, it is easy to check that every section of the wire contributes to the magnetic field lines in the same direction within the loop.

Q7. 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.

Q8. 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.

Q9. Explain the force on a current carrying conductor in a magnetic field. Write about the rule to find direction of this force. What are the devices in which current carrying conductors and magnetic fields are used?

Ans – When a current-carrying conductor is placed in a magnetic field, it experiences a force known as the magnetic force. The magnitude and direction of this force can be determined using the right-hand rule.

Right-Hand Rule for Force on a Current-Carrying 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.

The force experienced by the conductor is perpendicular to both the direction of the current and the magnetic field.

Devices in which current carrying conductors and magnetic fields are used are following

1. Electric Motors: Electric motors use the interaction between current-carrying conductors and magnetic fields to generate rotational motion.
2. Generators: In generators, the relative motion between conductors and magnetic fields induces an electromotive force (EMF) and generates electrical power.
3. Loudspeakers: The principle is applied in loudspeakers where a coil carrying an electric current interacts with a magnetic field to produce sound.
4. Galvanometers: Devices that measure small electric currents often utilize the interaction between a coil and a magnetic field.
5. Transformers: Transformers use the principles of electromagnetic induction to change voltage levels in electrical circuits.

Q10. 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.

Q11. 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.