Answer:
<em><u>Ohm's Law:</u></em>
------------------(1)
Where V is voltage, I is current and R is resistance.
Whereas,
P = I V --------------------(2)
Where P is power, I is current and V is Voltage.
<u>Putting (1) into (2)</u>
=> P = I (I R) [∴ V = I R]
=> P = I²R (Derived!)