Question

The magnetic field intensity (H) at the centre of a long solenoid having 'n' turns per unit length and carrying a current I, when no material is kept in it is (\(μ_0\) = permeability of free space)

• A. \(n/I\)
• B. \(nI\)
• C. \(μ_0I\)
• D. \(μ_0/nI\)

Hint:

H equals turns per unit length times current.

Answer 1

The Correct Option is B

Step 1: Ampere circuital law
A loop of length $l$ along the axis encloses $nlI$. Then $H l = nlI$, so $H = nI$. Option (B).

Final Answer:
nI. \[ \boxed{\text{(B)}\ nI} \]