# Electrical Energy Transferred

1. Jun 28, 2013

### Molly1235

Can anyone tell me how to calculate electrical energy transferred when you are given a voltage and a charge? I'm really stuck as we haven't covered this before :-/

2. Jun 28, 2013

### CWatters

Hopefully you recognise...

Power = Voltage * Current
and
Energy = Power * Time

So

Energy = Voltage * Current * Time

but

Current * Time = Charge

(Edit: or if you prefer Current = Charge/Time)

So

Energy = Voltage * Charge

3. Jun 28, 2013

### Molly1235

Ok, yeah I got as far as Energy = Voltage * current * time, but I'm afraid I don't understand how you got to energy = charge * voltage? (Probably being extremely dumb here...)

4. Jun 28, 2013

### CWatters

Ok so you got as far as ....

Energy = Voltage * Current * Time .......................... (eqn 1)

Think about what current is. Current is the amount of charge flowing past a point per second. Just like the current of a river is the amount of water flowing past per second.

So the definition of current is Charge/Time

Now in equation 1 above you can replace "Current" with "Charge/Time" to give

Energy = Voltage * (Charge/Time) * Time

Time cancels to leave

Energy = Voltage * Charge

5. Jun 28, 2013

### Molly1235

Oooh I understand now! Thank you very much!!