Question

In a fluorescent lamp choke (a small transformer) $100\text{V}$ of reverse voltage is produced when the choke current changes uniformly from $0.25\text{A}$ to $0$ in a duration of $0.025\text{ms}$. The self-inductance of the choke coil (in $\text{mH}$) is estimated to be .

Answer 1

Given $dI=0.25-0=0.25\text{A}$

$dt=0.025\text{ms}$

Induced voltage,
$E_{\text{ind}}=100\text{V}$

Self-inductance, L = ?
The induced emf in an inductor is,

$E_{\text{ind}}=\frac{d\varphi }{dt}$

$\Rightarrow 100=\frac{L(0.25-0)}{0.025\times {10}^{-3}}$

$\Rightarrow L={10}^{-3}H=10\text{mH}$