User:Inconspicuum/Physics (A Level)/Power

Power is a measure of how much potential energy is dissipated (i.e. converted into heat, light and other forms of energy) by a component or circuit in one second. This is due to a drop in the potential energy, and so the voltage, of charge. Power is measured in Watts (commonly abbreviated W), where 1 W is 1 Js-1. It can be calculated by finding the product of the current flowing through a component / circuit and the potential difference across the component / circuit. This gives us the equation:

$$P = \frac{E}{t} = IV$$

where P is the power dissipated (in W), E is the drop in potential energy (in Joules, J), t is the time taken (in s), I is the current (in A) and V is either potential difference or electromotive force (in V), depending on the component being measured.

Since power is the amount of energy changing form per. second, the amount of energy being given out each second will equal the power of the component giving out energy.

You should be able to substitute in values for I and V from other formulae (V=IR, Q=It) in order to relate power to resistance, conductance, charge and time, giving formulae like these:

$$P = I^2R$$

$$P = \frac{V^2}{R}$$

$$P = \frac{QV}{t}$$