In a circuit shown in fig. the heat produced in 5 ohm resistor due to a current flowing in it is 10 calories per second. The heat produced in 4 ohm resistor is

Resistance of upper branch, R₁ $=10\mathrm{\Omega }$
Resistance of lower branch, R₂  = 5 $\mathrm{\Omega }$
As they are connected in parallel, hence potential difference across each will be same = V
Given that $\frac{{\mathrm{V}}^2}{4\cdot 2{\mathrm{R}}_2}=10\mathrm{cal}/\sec$
$\therefore {\mathrm{V}}^2=4\cdot 2\times 10\times 5=210$
or $\mathrm{V}=\sqrt{\left(210\right)} \mathrm{volt}$
Current in 4 $\mathrm{\Omega }$ resistance
$=\left(\mathrm{V}/{\mathrm{R}}_1\right)=\{\sqrt{\left(210\right)}/10\}$
Heat produced $=\left({\mathrm{i}}^2\mathrm{R}/4\cdot 2\right)\mathrm{cal}/\sec$
$=\frac{210}{100}\times \frac{4}{4\cdot 2}=2\mathrm{cal}/\sec$