Moving Charges and Magnetism - Result Question 29

30. A cylindrical conductor of radius $R$ is carrying a constant current. The plot of the magnitude of the magnetic field, B with the distance, $d$, from the centre of the conductor, is correctly represented by the figure :

[2019]

(a)

(b)

(c)

(d)

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Answer:

Correct Answer: 30. (c)

Solution:

  1. (c) Inside $(d<R)$

Magnetic field inside conductor

$B=K d$

This is straight line passing through origin

At surface $(d=R)$ $B=\frac{\mu_0}{2 \pi} \frac{1}{d}$

Maximum at surface

Outside $(d>R)$

$B=\frac{\mu_0}{2 \pi} \frac{1}{d}$

or $\quad B \propto \frac{1}{d} \quad \therefore$ Hyperbolic