Question

The current element of the solenoid of turns 100, length 2m and current 0.5A is given by,

(a) 100 dx

(b) 200 dx

(c) 25 dx

(d) 50 dx

I had been asked this question in a national level competition.

My question is taken from Biot Savart Law topic in portion Magnetostics of Electromagnetic Theory

Answer 1

Correct answer is (c) 25 dx

The explanation is: The current element of the solenoid is given by NI dx/L. Put N = 100, I = 0.5 and L = 2 to get, I dx = 100 x 0.5 x dx/2 = 25 dx.