Solution of Chapter 13. Magnetic Effects of Electric Current (NCERT - Science Book)

Chapter Exercises

In Text Questions-Pg-224
In Text Questions-Pg-228
In Text Questions-Pg-229
In Text Questions-Pg-231
In Text Questions-Pg-233
In Text Questions-Pg-236
In Text Questions-Pg-237
In Text Questions-Pg-238
Exercise-Pg-240

In Text Questions-Pg-224

1

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

In Text Questions-Pg-228

1

Draw magnetic field lines around a bar magnet.
2

List the properties of magnetic lines of force.
3

Why don't two magnetic lines of force intersect with each other?

In Text Questions-Pg-229

1

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.
2

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

In Text Questions-Pg-231

1

Which of the following property/properties 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

A small aluminium rod AB is suspended horizontally from a stand by the ends of two connecting wires as shown in the Figure given here. A horseshoe magnet is placed in such a way that north pole of the magnet is vertically below and its south pole vertically above the aluminium rod. The aluminium rod is connected in series with a battery, a key and a rheostat. How do you think the displacement of rod AB will be affected if:

(i) current in rod AB is increased?


(ii) a stronger horseshoe magnet is used?


(iii) length of the rod AB is increased?
3

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

In Text Questions-Pg-233

1

State Flemings left-hand rule.
2

What is the principle of an electric motor?
3

What is the role of the split ring in an electric motor?

In Text Questions-Pg-236

1

State different ways to induce current in a coil.

In Text Questions-Pg-237

1

State the principle of an electric generator.
2

Name some sources of direct current.
3

Which sources produce alternating current?
4

Choose the correct option:

A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced cum changes once in each:


(a) two revolutions


(b) one revolution


(c) half revolution


(d) one-fourth revolution

In Text Questions-Pg-238

1

Name two safety measures commonly use in electric circuits and appliances.
2

An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
3

What precautions should be taken to avoid the overloading of domestic electric circuits?

Exercise-Pg-240

1

Which of the following correctly describes the magnetic field near a long straight wire?
2

The phenomenon of electromagnetic induction is:
3

The device used for producing electric current is called a:
4

The essential difference between an AC generator and a DC generator is that:
5

At the time of short circuit, the current in the circuit:
6

State whether the following statements are true or false:

(a) An electric motor converts mechanical energy into electrical energy.


(b) An electric generator works on the principle of electromagnetic induction


(c) The field at the centre of a long circular coil carrying current will be parallel straight lines


(d) A wire with a green insulation is usually the live wire of an electric supply
7

List three sources of magnetic fields.
8

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.
9

When is the force experienced by a current-carrying conductor placed in a magnetic field largest ?
10

Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
11

Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?
12

Name some devices in which electric motors are used.
13

A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is

(i) pushed into the coil


(ii) held stationary inside the coil


(iii) withdrawn from inside the coil.
14

Two circular coils A and B are placed close to each other. If the current in the coil A is changed, will some current be induced in the coil B ? Give reason.
15

State the rule to determine the direction of a:

(i) magnetic field produced around a straight conductor carrying current.


(ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it.


(iii) current induced in a straight conductor moving in a magnetic field.
16

Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?
17

When does an electric short circuit occur?
18

Why is it necessary to earth metallic appliances? What is the function of an earth wire?