Moving Charges and Magnetism - Result Question 50

51. A straight wire of diameter $0.5 mm$ carrying a current of $1 A$ is replaced by another wire of 1 $mm$ diameter carrying same current. The strength of magnetic field far away is

[1995, 97, 99]

(a) twice the earlier value

(b) same as the earlier value

(c) one-half of the earlier value

(d) one-quarter of the earlier value

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Answer:

Correct Answer: 51. (b)

Solution:

  1. (b) $B=\frac{\mu_0 i}{2 \pi r}$ and so it is independent of thickness.

The current is same in both the wires, hence magnetic field induced will be same.