The self-inductance of solenoid of length $31.4 \mathrm{~cm}$, area of cross section $10^{-3} \mathrm{~m}^2$…

The self-inductance of solenoid of length $31.4 \mathrm{~cm}$, area of cross section $10^{-3} \mathrm{~m}^2$ having total number of turns 500 will be nearly $\left[\mu_0=4 \pi \times 10^{-7}\right.$ SI unit $]$
  1. $3 \times 10^{-3} \mathrm{H}$
  2. $1 \times 10^{-3} \mathrm{H}$
  3. $2 \times 10^{-3} \mathrm{H}$
  4. $4 \times 10^{-3} \mathrm{H}$

Solution

$\begin{aligned} & \ell=31.4 \mathrm{~cm}=0.314 \mathrm{~m} \\ & \mathrm{~A}=10^{-3} \mathrm{~m}^2, \mathrm{~N}=500 \end{aligned}$ Self-inductance, $L=\mu_0 n^2 \ell A$ $\begin{aligned} & =\frac{\mu_0 \mathrm{~N}^2 \mathrm{~A}}{\ell}, \quad \text { where } \mathrm{n}=\frac{\mathrm{N}}{\ell} \\ & =\frac{4 \pi \times 10^{-7} \times(500)^2 \times 10^{-3}}{0.314} \\ & =\frac{4 \times 3.14 \times 25 \times 10^{-6}}{0.314} \\ & =10^{-3} \mathrm{H} \end{aligned}$

Asked in: MHT CET 2021 (24 Sep Shift 1)

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