Question

If a long hollow copper pipe carries a direct current, the magnetic field associated with the current will be ______.

Options

• Only inside the pipe
• Only outside the pipe
• Neither inside nor outside the pipe
• Both inside and outside the pipe

Answer 1

If a long hollow copper pipe carries a direct current, the magnetic field associated with the current will be only outside the pipe.

Explanation:

The current I threading the closed path at a point inside the pipe is zero.

So, B = `(mu_0)/(4pi) = (2l)/r` = 0  ......`(because I = 0)`