The electrical power of a device is the rate at which it transfers energy. It is measured in watts (W). You can find it from the current through the device and the potential difference across it: electrical power = current × potential difference, or P = I × V. Here P is in watts (W), I is in amperes (A) and V is in volts (V). A kettle that draws 10 A from a 230 V supply has a power of 10 × 230 = 2300 W.
Ohm's law says that V = I × R, where R is the resistance in ohms (Ω). If you put this in place of V in the equation P = I × V, you get a second equation: electrical power = current squared × resistance, or P = I2 × R. Here I2 is in A2.
For example, a current of 2 A in a resistor of 5 Ω gives P = 22 × 5 = 4 × 5 = 20 W. If the current is doubled to 4 A, the resistance stays the same and the power becomes 42 × 5 = 80 W. Doubling the current makes the power four times bigger, because the current is squared.