If a long hollow copper pipe carries a current, then magnetic field is produced
A
Only inside the pipe
B
Only outside the pipe
C
Neither inside nor outside the pipe
D
Both inside and outside the pipe
AIPMT 1999, Easy
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B
Only outside the pipe
b (b)Because for inside the pipe $i = 0$
$\therefore B = \frac{{{\mu _0}i}}{{2\pi r}} = 0$
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