Magnetic Effects of Electric Current Set-1

Question 1

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

Accepted Answer

The field consists of concentric circles centered on the wire.

Answer

The field consists of straight lines perpendicular to the wire.

Answer

The field consists of straight lines parallel to the wire.

Answer

The field consists of radial lines originating from the wire.

Question 2

The phenomenon of electromagnetic induction is:

Accepted Answer

Producing induced current in a coil due to relative motion between a magnet and the coil.

Answer

The process of charging a body.

Answer

The process of generating magnetic field due to a current passing through a coil.

Answer

The process of rotating a coil of an electric motor.

Question 3

The device used for producing electric current is called a:

Accepted Answer

Generator

Answer

Galvanometer

Answer

Ammeter

Answer

Motor

Question 4

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

Accepted Answer

Increases heavily

Answer

Reduces substantially

Answer

Does not change

Answer

Vary continuously

Question 5

A soft iron bar is introduced inside a current-carrying solenoid. The magnetic field inside the solenoid will:

Accepted Answer

Increase

Answer

Decrease

Answer

Remain same

Answer

Become zero

Question 6

The north pole of a compass needle points towards the:

Accepted Answer

Both (B) and (C)

Answer

Magnetic North Pole of the Earth

Answer

Geographic North Pole of the Earth

Answer

Magnetic South Pole of the Earth

Question 7

What is the shape of the magnetic field lines inside a current-carrying solenoid?

Accepted Answer

Parallel straight lines

Answer

Circular

Answer

Elliptical

Answer

Non-uniform curves

Question 8

A positively charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is:

Accepted Answer

Upward

Answer

Towards south

Answer

Towards east

Answer

Downward

Question 9

The strength of the magnetic field $B$ at the center of a circular coil of radius $R$ is:

Accepted Answer

Inversely proportional to $R$

Answer

Directly proportional to $R$

Answer

Directly proportional to $R^2$

Answer

Inversely proportional to $R^2$

Question 10

Which rule is used to find the direction of force on a current-carrying conductor in a magnetic field?

Accepted Answer

Fleming’s Left-Hand Rule

Answer

Right-Hand Thumb Rule

Answer

Fleming’s Right-Hand Rule

Answer

Faraday’s Law

Question 11

The potential difference between the live wire and the neutral wire in India is:

Accepted Answer

$220	ext{ V}$

Answer

$110	ext{ V}$

Answer

$440	ext{ V}$

Answer

$0	ext{ V}$

Question 12

If the current $I$ in a straight wire is doubled, the magnetic field $B$ at a distance $r$ from it:

Accepted Answer

Becomes double

Answer

Becomes half

Answer

Becomes four times

Answer

Remains the same

Question 13

Why are magnetic field lines never found to cross each other?

Accepted Answer

At the point of intersection, the compass would point in two directions, which is impossible.

Answer

They are parallel to each other.

Answer

They originate from the same pole.

Answer

The field is too weak at the crossing point.

Question 14

An electron enters a magnetic field at right angles to it. The direction of force acting on the electron will be:

Accepted Answer

Into the page

Answer

To the right

Answer

To the left

Answer

Out of the page

Question 15

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

Accepted Answer

AC generator has slip rings while the DC generator has a commutator.

Answer

AC generator has an electromagnet while a DC generator has permanent magnet.

Answer

DC generator will generate a higher voltage.

Answer

AC generator will generate a higher voltage.

Question 16

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

Accepted Answer

Half revolution

Answer

Two revolutions

Answer

One revolution

Answer

One-fourth revolution

Question 17

The safety device used for protecting home appliances from burning due to short circuit or overloading is:

Accepted Answer

Fuse

Answer

Earth wire

Answer

Voltmeter

Answer

Galvanometer

Question 18

The magnetic field produced by a solenoid is similar to that of a:

Accepted Answer

Bar magnet

Answer

Horseshoe magnet

Answer

Straight conductor

Answer

Circular loop

Question 19

Which of the following factors does NOT affect the strength of the magnetic field of a solenoid?

Accepted Answer

Length of the connecting wires

Answer

Number of turns in the solenoid

Answer

Magnitude of current

Answer

Nature of core material

Question 20

For a current in a long solenoid, the N- and S-poles are created at the two ends. Among the following statements, the incorrect statement is:

Accepted Answer

The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.

Answer

The field lines inside the solenoid are in the form of straight lines.

Answer

The strong magnetic field produced inside the solenoid can be used to magnetize a piece of magnetic material.

Answer

The N- and S-poles exchange positions if the direction of current is reversed.

Question 21

In Fleming’s Right-Hand Rule, the middle finger indicates the direction of:

Accepted Answer

Induced current

Answer

Magnetic field

Answer

Motion of conductor

Answer

Applied force

Question 22

The work done by a magnetic field on a moving charge is:

Accepted Answer

Zero

Answer

Always positive

Answer

Always negative

Answer

Depends on the angle

Question 23

An electric motor is a device which converts:

Accepted Answer

Electrical energy into mechanical energy

Answer

Mechanical energy into electrical energy

Answer

Chemical energy into electrical energy

Answer

Mechanical energy into light energy

Question 24

The color of the insulation for the earth wire is usually:

Accepted Answer

Green

Answer

Red

Answer

Black

Answer

Yellow

Question 25

Commercial motors do NOT use:

Accepted Answer

A permanent magnet to rotate the armature.

Answer

An electromagnet to rotate the armature.

Answer

Effectively large number of turns of conducting wire in the current-carrying coil.

Answer

A soft iron core on which the coil is wound.

Question 26

Magnetic lines of force outside a bar magnet run from:

Accepted Answer

North to South

Answer

South to North

Answer

East to West

Answer

West to East

Question 27

A Galvanometer is used to:

Accepted Answer

Detect the presence of current

Answer

Measure high currents

Answer

Measure potential difference

Answer

Measure resistance

Question 28

Overloading happens when:

Accepted Answer

All of the above.

Answer

Many appliances are connected to a single socket.

Answer

The insulation of wires is damaged.

Answer

There is a hike in the supply voltage.

Question 29

The magnitude of the force experienced by a current-carrying conductor in a magnetic field is maximum when the angle between the current and the field is:

Accepted Answer

$90^\circ$

Answer

$0^\circ$

Answer

$45^\circ$

Answer

$180^\circ$

Question 30

Which wire is connected to a metal plate deep in the Earth?

Accepted Answer

Earth wire

Answer

Live wire

Answer

Neutral wire

Answer

Fuse wire

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Magnetic Effects of Electric Current Set-1

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