Multiple Choice

A hollow tube is carrying an electric current along its length distributed uniformly over its surface. The magnetic field :

Aincreases linearly from the axis to the surface
Bis constant inside the tube
Correct Answer
Cis zero at the axis
Correct Answer
Dis zero just outside the tube

Solution

Since current is on the surface only, any amperian loop drawn inside the hollow portion of the cylinder will not contain any current.
$$\therefore$$ magnetic field is zero inside the hollow portion.

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