Question

The magnetic flux near the axis and inside the air core solenoid of length $60\, cm$ carrying current ‘I’ is $1.57 \times 10^{-6} \, Wb$. Its magnetic moment will be (cross-sectional area of a solenoid is very small as compared to its length, $\mu_0 = 4 \pi \times 10^{- 7} $ SI unit)

• A. $ 0.25 \, A$
• B. $ 0.50 \, A$
• C. $ 0.75 \, A$
• D. $ 1 \, A$

Answer 1

Answer: (C)

Magnetic induction inside the solenoid
$B =\frac{\mu_{0} NI }{ L }$
Magnetic Flux,$\phi= BA =\frac{\mu_{0} NIA }{ L }$
Magnetic moment $= NIA =\frac{\phi L }{\mu_{0}}$
$=\frac{1.57 \times 10^{-6} \times 0.6}{4 \times 3.141 \times 10^{-7}}$
$=0.75 \,Am ^{2}$