# In a fluorescent lamp choke (a small transformer)

Question:

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

Solution:

(10) Given $d I=0.25-0=0.25 \mathrm{~A}$

$d t=0.025 \mathrm{~ms}$

Induced voltage

$E_{\text {ind }}=100 \mathrm{v}$

Self-inductance, $L=$ ?

Using, $E_{\text {ind }}=\frac{\Delta \phi}{\Delta t}$

$\Rightarrow 100=\frac{L(0.25-0)}{.025 \times 10^{-3}}$

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