Magnetic Effects of Electric Current Test

Result

Magnetic Effects of Electric Current Test - 24

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Question 1
1 / -0

The magnetic field inside a solenoid is:

A
infinite

B
zero

C
uniform

D
non-uniform

Solution

The magnetic field inside a solenoid is uniform.
Question 2
1 / -0

The following diagram shows a spiral coil wound on a hollow cardboard tube AB. A magnetic compass is placed close to it. Current is switched on by closing the key. What will be the polarity at the ends A and B?

A
A - north pole, B - south pole

B
A - south pole, B -north pole

C
A - south pole, B - south pole

D
A - north pole, B - north pole

Solution

The polarity of the magnetic field (that is, which end is magnetic-north or magnetic-south) can easily be found from the Right hand thumb rule. If we hold the device in our right hand, so that the fingers curl around it in the direction of the conventional current flow, then the thumb will point to the north pole of the magnet. Also, a solenoid when suspended freely aligns itself in the north-south direction, thus behaving like a magnet. One end of the solenoid acts like a north pole and the other end the south pole.

The polarity of the solenoid AB can be changed by reversing the direction of the current. If we imagine that we are facing the coil end-on, then if the current flows in a clockwise direction, we are looking at the south pole. If the current flows in an anticlockwise direction, we are looking at the north pole.
When a magnetic compass is brought closer to A end of the solenoid, the needle deflects away from the north-south direction as like poles repel.

Hence, the polarity at A is north and polarity at B is south.
Question 3
1 / -0

The adjacent diagram shows a small magnet placed near a solenoid AB with its north pole N near the end A. Current is switched on in the solenoid by pressing the key K. State the polarity at the ends A and B:

A
A - south pole, B - north pole

B
A - south pole, B - south pole

C
A - north pole, B - north pole

D
A - north pole, B - south pole

Solution

The polarity of the magnetic field (that is, which end is magnetic-north or magnetic-south) can easily be found from the Right hand thumb rule. If we hold the device in our right hand, so that the fingers curl around it in the direction of the conventional current flow, then the thumb will point to the north pole of the magnet. Also, a solenoid when suspended freely aligns itself in the north-south direction, thus behaving like a magnet. One end of the solenoid acts like a north pole and the other end the south pole.

Hence, A - south pole, B - north pole.
Question 4
1 / -0

The adjacent diagram shows a small magnet placed near a solenoid AB with its north pole N near the end A. Current is switched on in the solenoid by pressing the key K. Magnet will get :

A
Attracted

B
Repelled

C
No change

D
can't say

Solution

Since A - south pole and B - north pole.
The magnet will get attracted as unlike poles attract to each other.
Question 5
1 / -0

In the following figure, three path of a particle crossing a nucleus N are shown. The correct path is

A
a and c

B
a and b

C
a, b, and c

D
only a

Solution
Question 6
1 / -0

A very long straight wire carries a current $$I$$. At the instant when a charge $$+Q$$ at point $$P$$ has velocity $$\overrightarrow{v}$$, as shown in figure, the force on charge is

A
along OY

B
opposite to OY

C
along OX

D
opposite to OX

Solution

The magnetic field at $$P$$ is inwards due to a straight long conductor. Fleming's left hand rule gives the direction along $$oy$$.
Question 7
1 / -0

A pair of slip rings is used in -

A
Ac generator

B
Dc generator

C
Ac motor

D
Dc motor

Solution

The function of a slip ring in an AC generator is that these are the hollow rings that are connected to the ends of the armature coil. They help in the rotation of the coil. A slip ring in an electric motor is used as an electrical joint to transmit power. It acts as a bridge between a still component and a rotating element.
Question 8
1 / -0

According to Fleming's Left Hand Rule, the ....... points in the direction of the magnetic field.

A
Thumb

B
Forefinger

C
Second finger

D
Middle finger

Solution
Question 9
1 / -0

An electron having a charge $$e$$ moves with a velocity $$v$$ in X-direction. A magnetic field acts on it in Y-direction. The force on the electron acts in

A
positive direction of Y-axis

B
negative direction of Y-axis

C
positive direction of Z-axis

D
negative direction of Z-axis

Solution

The direction of force on the electron can be found using the Fleming's left hand rule. As electron is moving in positive x-direction, so the current is moving in negative x-direction ( the direction of your middle finger) and the magnetic field acts on positive Y-direction ( the direction of your index finger) then thumb will be in negative Z-direction which is the direction of force.
Question 10
1 / -0

The following diagram shows a spiral coil wound on a hollow cardboard tube AB. A magnetic compass is placed close to it. Current is switched on by closing the key. How will the compass needle be affected ? Give reason.

A
The north pole of compass needle will deflect towards north.

B
The north pole of compass needle will deflect towards east.

C
The north pole of compass needle will deflect towards west.

D
The north pole of compass needle will deflect towards south.

Solution

The polarity of the magnetic field (that is, which end is magnetic-north or magnetic-south) can easily be found from the Right hand thumb rule. If we hold the solenoid in our right hand, so that the fingers curl around it in the direction of the conventional current flow, then the thumb will point to the north pole of the magnet.
When magnetic compass with the north end is brought closer to the A end of the solenoid AB, the needle deflects towards the west, that is away from the solenoid because the magnetic compass that is pointing in the direction of the earth's magnetic field, i.e. north- south direction repels with the north pole of current carrying solenoid.