100 J of heat is produced per second in a 4 Ω resistor. What is the potential difference across the resistor?

The potential difference across the resistor is 20 V.
Given,
Heat,$\mathit{ H }= 100\mathit{ J}$
Time, $\mathit{t }= 1\mathit{ s}$
Resistance, $\mathit{R }= 4\mathit{ \Omega }$
We know that the heat $\left(H\right)$ is given by the relation:
$\mathrm{H}={\mathrm{I}}^2\mathrm{Rt}$ 
On substituting the given values, we get
$\Rightarrow 100=I^2\times 4\times 1$
$\Rightarrow I^2=25$
$\Rightarrow \mathit{I }= 5\mathit{ A}$
From the Ohm's law, we get
$\Rightarrow V=\mathit{IR}$
On substituting the values, we get
$\Rightarrow V=5\times 4$ 

$\Rightarrow \mathrm{V}=20 \mathrm{v}$