Class 10 Science

Chapter 12 Solutions — Magnetic Effects of Electric Current

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Solutions

Overview

Step-by-step NCERT solutions for Magnetic Effects of Electric Current (Chapter 12, CBSE Class 10 Science) — the full working for every question, not just the final answer. You can also read the Magnetic Effects of Electric Current textbook chapter.

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What these solutions cover

All 34 questions in Magnetic Effects of Electric Current are solved in the PDF. Here's what's inside, exercise by exercise:

Magnetic Field and Field Lines

Why does a compass needle get deflected when brought near a bar magnet?

Magnetic Field due to a Current-Carrying Conductor

Draw magnetic field lines around a bar magnet.
List the properties of magnetic field lines.
Why don't two magnetic field lines intersect each other?

Magnetic Field due to a Current through a Straight Conductor

Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
The magnetic field in a given region is uniform. Draw a diagram to represent it.
3.
Choose the correct option. The magnetic field inside a long straight solenoid-carrying current
- (a) is zero.
- (b) decreases as we move towards its end.
- (c) increases as we move towards its end.
- (d) is the same at all points.

Force on a Current-Carrying Conductor in a Magnetic Field

1.
Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)
- (a) mass
- (b) speed
- (c) velocity
- (d) momentum
2.
In Activity 13.7, how do we think the displacement of rod AB will be affected if
- (i) current in rod AB is increased;
- (ii) a stronger horse-shoe magnet is used; and
- (iii) the length of the rod AB is increased?

Electric Motor

1.
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
- (a) towards south
- (b) towards east
- (c) downward
- (d) upward

Electromagnetic Induction

State Fleming's left-hand rule.
What is the principle of an electric motor?
What is the role of the split ring in an electric motor?

Electric Generator

Explain different ways to induce current in a coil.

Domestic Electric Circuits

State the principle of an electric generator.
When does an electric short circuit occur?
What is the function of an earth wire? Why is it necessary to earth metallic appliances?

End-of-Chapter Exercise

1.
Which of the following correctly describes the magnetic field near a long straight wire?
- (a) The field consists of straight lines perpendicular to the wire.
- (b) The field consists of straight lines parallel to the wire.
- (c) The field consists of radial lines originating from the wire.
- (d) The field consists of concentric circles centred on the wire.
2.
At the time of short circuit, the current in the circuit
- (a) reduces substantially.
- (b) does not change.
- (c) increases heavily.
- (d) varies continuously.
3.
State whether the following statements are true or false.
- (a) The field at the centre of a long circular coil carrying current will be parallel straight lines.
- (b) A wire with a green insulation is usually the live wire of an electric supply.
List two methods of producing magnetic fields.
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
Draw the pattern of magnetic field lines of a current-carrying solenoid. What does the pattern of field lines inside the solenoid indicate?
Compare and contrast a bar magnet and an electromagnet.
An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for your response.
9.
Explain the following.
- (a) Why is the tungsten used almost exclusively for filament of electric lamps?
- (b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
- (c) Why is the series arrangement not used for domestic circuits?
- (d) How does the resistance of a wire vary with its area of cross-section?
- (e) Why are…
What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?
11.
How can three resistors of resistances 2 ohm, 3 ohm, and 6 ohm be connected to give a total resistance of
- (a) 4 ohm,
- (b) 1 ohm?
12.
What is
- (a) the highest,
- (b) the lowest total resistance that can be secured by combinations of four coils of resistance 4 ohm, 8 ohm, 12 ohm, 24 ohm?
Why does the cord of an electric heater not glow while the heating element does?
Compute the heat generated while transferring 96000 coulombs of charge in one hour through a potential difference of 50 V.
An electric iron of resistance 20 ohm takes a current of 5 A. Calculate the heat developed in 30 s.
What determines the rate at which energy is delivered by a current?
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.

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