S-Cool Revision Summary

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...

Work Done (or Energy) and Power Equations

The definition of voltage tells us that Copyright S-cool

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:

Copyright S-cool

So, Power = V I (Learn this!)

Power and Resistance Equations

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

or

Copyright S-cool

Learn these!

The kWhr

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