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, then new value of the magnetic field is

• A. B
• B. 2B
• C. 4B
• D. B/2

Answer 1

Answer: (A)

B

Answer 2

B = m₀ni B' = m₀ $\left( \frac { \mathrm { n } } { 2 } \right)$ (2i) = B