Energy and Power

Power is the rate at which energy is transferred

Power (W) = Energy Transferred (J) / time (s)          P = W / t

A 100W bulb, for example, transfers 100J of energy every second from electrical into heat and light.

Now we have a number of quantities and several equations. By rearranging and combining them we can generate several other useful equations.

Quantity	Charge	Current	Voltage	Resistance	Energy Transferred	Power
Symbol	Q	I	V	R	W	P
Units	Coulombs	Amps	Volts	Ohms	Joules	Watts
Symbol for units	C	A	V		J	W

You should make an effort to learn the table above and the equations in red boxes below. They are the tools you will need to solve a lot of problems and you really should know them by heart.