Basic Electrical Engineering Questions and Answers – Magnetic Field Due to an Electric Current

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This set of Basic Electrical Engineering Interview Questions and Answers for Experienced people focuses on “Magnetic Field Due to an Electric Current”.

1. The force existing between two infinite parallel conductors is inversely proportional to ________
b) Current in one of the conductors
c) The product of the current in the two conductors
d) The distance between the two conductors

Explanation: When current is flowing in two different conductors, the force between the two conductors is directly proportional to the product of the current in the two conductors and inversely proportional to the distance between the two conductors.

2. When the distance of operation between the two conductors increases, what happens to the force between the two conductors?
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero

Explanation: When the distance of separation increases, the force between the two conductors decrease because the force between two conductors is inversely proportional to the distance of separation between them.

3. Magnetic field at a point d distance away from long wire due to electric current i in it is ____________
a) µ0i/2r
b) µ0i/r
c) µ0i/2πr
d) µ0i/πr

Explanation: Magnetic field at distance d from long wire with carrying current i is given by-
B = µ0i/2πr.
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4. 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

Explanation: Force of infinite conductor is given by Bil if B, i, l are mutually perpendicular
F/l = Bi = µ0i1i2/2πd if d is separation of two infinite parallel conductors.

5. 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

Explanation: Force of the infinite conductor is given by Bil if B, i, l are mutually perpendicular
F/l = Bi = µ0i1i2/2πd if d is separation of two infinite parallel conductors. It doesn’t depend on the radius of conductor so force remains the same.

6. If current of conductor increases, what is the effect on the force?
a) increases
b) decreases
c) remain same
d) become zero

Explanation: Force of infinite conductor is given by Bil if B, i, l are mutually perpendicular
F/l = Bi = µ0i1i2/2πd if d is separation of two infinite parallel conductors. So, as current increases force increases.

7. If length of current carrying conductor increases, what is the effect on the force?
a) increases
b) decreases
c) remain same
d) become zero

Explanation: Force of infinite conductor is given by Bil if B, i, l are mutually perpendicular
F/l = Bi = µ0i1i2/2πd if d is a separation of two infinite parallel conductors. So, as length of conductor increases force increases.

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