Moving Charges and Magnetism - Result Question 52
53. The magnetic field at a distance $r$ from a long wire carrying current $i$ is 0.4 tesla. The magnetic field at a distance $2 r$ is
[1992]
(a) 0.2 tesla
(b) 0.8 tesla
(c) 0.1 tesla
(d) 1.6 tesla
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Answer:
Correct Answer: 53. (a)
Solution:
$ \text{ (a) } B=\frac{\mu_0 i}{2 \pi r} \text{ or } B \propto \frac{1}{r} $
When $r$ is doubled, the magnetic field becomes half, i.e., now the magnetic field will be $0.2 T$.
