Question

The magnetic flux near the axis and inside the air core solenoid of length $60$ cm carrying current ${}^{\prime }{I}^{\prime }$ 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, ${\mu }_0=4\pi \times {10}^{-7}SIunit)$

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

Answer 1

The correct option is C $0.75A$

Magnetic induction inside the solenoid

$B=\frac{{\mu }_{0}NI}{L}$

Magnetic Flux , $\varphi =BA=\frac{{\mu }_{0}NIA}{L}$

Magnetic moment = $NIA=\frac{\varphi L}{{\mu }_0}=\frac{1.57\times {10}^{-6}\times 0.6}{4\times 3.141\times {10}^{-7}}=0.75A{m}^2$