Consider a long solenoid of length l and radius r. If n is the number of turns per unit length and 0 is the permeability of free space, the inductance of the solenoid is :
- 2 0 n2 r2 l
- 0 n2 r2 l
- 0 n2 r2 l
- ( 0/2 )n2 r2 l
Answer
(2) 0 n2 r2 l
Solution
The self-inductance of a solenoid is given by:
L = 0 n2 A l
where A is the cross-sectional area, A = r2.
Substituting A:
L = 0 n2 r2 l
Answer: (2)