Moving Charges and Magnetism - Result Question 42
43. A long solenoid carrying a current produces a magnetic field $B$ along its axis. If the current is double and the number of turns per $cm$ is halved, the new value of the magnetic field is [2003]
(a) $4 B$
(b) $B / 2$
(c) $B$
(d) $2 B$
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Answer:
Correct Answer: 43. (c)
Solution:
(c) $B=\mu_0 n i$
$B_1=(\mu_0)(\frac{n}{2})(2 i)=\mu_0 n i=B$
$\Rightarrow B_1=B$
