S-Cool Revision Summary
As electricity is all about energy, there are a few energy and power equations that you need to be able to derive and use...
The definition of voltage tells us that
So, W = VQ
The definition of current tells us that, Q = It
So, W = V I t (Learn this!)
Of course, we already know that:
So, Power = V I (Learn this!)
From Ohm's law we know that V = IR. If this equation is substituted into the equation P = IV we can get two new equations:
Power = I2R
Electrical energy is measured in units of the kWhr so that people can be charged for the amount that they use. At the moment, 1 kWhr of energy costs about 7p.
energy = power x time
kWhr = kW x hr