Fig. shows three similar lamps L₁, L₂, and L₃

connected across a power supply. If the lamp L₃. fuses, how will the light emitted by L₁, and L₂, change ?

Let R be the resistance of each lamp. If E be the applied the circuit I, is given by
${\mathrm{i}}_1=\frac{\mathrm{E}}{\mathrm{R}+(\mathrm{R}/2)}=\frac{2\mathrm{E}}{3\mathrm{R}}$
Current flowing through L₂ or L₃
$=\frac{1}{2}\left[\frac{2\mathrm{E}}{3\mathrm{R}}\right]=\frac{\mathrm{E}}{3\mathrm{R}}$
When L₃ is fused, the whole current flows through L₁ and L₂. Thus
${\mathrm{i}}_2=\frac{\mathrm{E}}{2\mathrm{R}}$
So, current through L₁ decreases and through L₂ increases.