POWER

The Power dissipated in a resistor R by a current (I) passing through it is given a P=IV, where V is the potential difference across the resistor. This equation can be expressed in a number of alternative ways by substitutions using
R= V/I

Power = ( Current) I x Voltage (V)

Power Formulae
1. (Power) P=IxV
2. (Power) P= V^2/R
3. (Power) P= I^(2 )R

As (Current) I= V/R replacing I for V/R gives
P=IV = V/R x V
P= V^2/R

As (Voltage) V=IR replacing V for (IR) gives
P=IV =I x (IR)
P=I^(2 )R

Substituting,
You can work out for resistance when you have the Power dissipated and Voltage supply using power formulae,

Since, (Power) P= V^2/R
Therefore, (Resistance) R= V^2/P
You can also work out for the resistance when you have the Power dissipated and the Current, using power formulae,

Since, (Power) P=I^(2 )R

Therefore, (Resistance) R=P/I^2