Direction of Magnetic Field MCQ [Free PDF] – Objective Question Answer for Direction of Magnetic Field Quiz

21. The force per unit length existing between two infinite parallel conductors is given by ___________

A. µ0i1i2/2πd
B. µ0i1i2/2d
C. µ0i1/2πdi2
D. µ0i1i2/d

Answer: A

Force of the infinite conductor is given by Bil if B, I, and l are mutually perpendicular

F/l = Bi = µ0i1i2/2πd

where d is the separation of two infinite parallel conductors.

 

22. If the radius of the current-carrying conductor increases, what is the effect on the force?

A. increases
B. decreases
C. remain same
D. become zero

Answer: C

Force of the infinite conductor is given by Bil if B, I, and l are mutually perpendicular

F/l = Bi = µ0i1i2/2πd

where

d is the separation of two infinite parallel conductors. It doesn’t depend on the radius of the conductor so the force remains the same.

 

23. If the current of the conductor increases, what is the effect on the force?

A. increases
B. decreases
C. remain same
D. become zero

Answer: A

The Force of the infinite conductor is given by Bil

where

B, I, and l are mutually perpendicular

F/l = Bi = µ0i1i2/2πd

where

d is the separation of two infinite parallel conductors. So, as current increases force increases.

 

24. If the length of the current-carrying conductor increases, what is the effect on the force?

A. increases
B. decreases
C. remain same
D. become zero

Answer: A

Force of the infinite conductor is given by Bil where

B, I, and l are mutually perpendicular

F/l = Bi = µ0i1i2/2πd

Where

d is a separation of two infinite parallel conductors. So, as the length of the conductor increases force increases.

 

25. The magnetic field strength of a solenoid can be increased by inserting which of the following materials as the core?

A. Copper
B. Silver
C. Iron
D. Aluminium

Answer: C

The Magnetic field of a solenoid increases when we insert an iron core because iron is a ferromagnetic material and ferromagnetic materials help in increasing the magnetic property.

 

26. If a coil is wound around a steel core and electric current is passed through the coil, the steel core acts as a?

A. Electromagnet
B. Permanent magnet
C. Neither electromagnet nor permanent magnet
D. Either electromagnet or permanent magnet

Answer: B

When a coil is wound around a steel core, the steel core behaves like a permanent magnet because it is a ferromagnetic material and once it becomes magnetic it does not lose its magnetic property.

 

27. What is the formula for the magnetic field due to a solenoid?

A. μnI
B. μn2
C. μNI
D. μN2I2

Answer: A

The magnetic field due to a solenoid is:
B = μnI,

where

μ is the permeability

n is the number of turns per unit length and

I is the current in the solenoid.

 

28. What happens to the magnetic field in the solenoid when the number of turns increases?

A. Increases
B. Decreases
C. Remains constant
D. Becomes zero

Answer: A

The magnetic field of a solenoid is directly proportional to the number of turns in it. Hence as the number of turns increases, the magnetic field also increases.

 

29. What happens to the magnetic field in the solenoid when the current increases?

A. Increases
B. Decreases
C. Remains constant
D. Becomes zero

Answer: A

The magnetic field of a solenoid is directly proportional to the current in it. Hence as the current increases, the magnetic field also increases.

 

30. What happens to the magnetic field in the solenoid when the length of the solenoid increases?

A. Increases
B. Decreases
C. Remains constant
D. Becomes zero

Answer: B

The magnetic field of a solenoid is inversely proportional to the length. Hence as the length increases, the magnetic field decreases.

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