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 vlaue of the magnetic field is
A. 2B
B. B/2
C. B
D. 4B

Answer 1

Correct Answer - C
`B prop nIbecause (B_2)/(B_1)=(n_2)/(n_1)(I_2)/(I_1)=(2n_1)/(n_1)(I_1)/(2I_1)`
`therefore B_2=B_1=B`