Question

A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved the new value of the magnetic field is

• A. $B/2$
• B. B
• C. 2 B
• D. 4 B

Answer 1

Answer: (B)

B

Answer 2

$B =\mu_{0} ni ; n '=\frac{ n }{2} ; i '=2 i$
$\Rightarrow B '= B$