Question

A long solenoid has a radius a and number of turns per unit length is n. If it carries a current i, then the magnetic field on its axis is directly proportional to

• A. ani
• B. ni
• C. $\frac { n i } { a }$
• D. $n ^ { 2 } i$

Answer 1

Answer: (B)

ni

Answer 2

Because $B \propto n i$.