A Level physics question

[AngloScot]

I'm stuck, please help! The question is

'What's the total energy carried by 5x10^17 electrons that have been accelerated by a potential difference of 1 kV in a) eV. B) J ?

Can someone give me a clue how to start this question please?

[fo3nix]

OK, so:

total energy of an electron E = e V (in joules, this is e x V)

where V = voltage, e = electron charge, 1.6x10^-19 C

so to find E, just multiply 1x10^3V by the total number of electrons, 5x10^17.

To find energy in eV, then its 5x10^17.

The latter (finding the eV) is trivial, from the definition of an eV, or electronvolt. 1 eV is the energy gained by an electron moving 1m through a potential difference of 1V.

[AngloScot]

Thanks alot mate :)

How do you get from eV to J though? I must be missing something simple here, can you please explain so it is clear to me. Thanks again.

[AngloScot]

I get it now... The answer in Joules is the answer in eV multiplied by 1.6x10^-19 durrrrrrrrr lol. im glad i cleared that up before anyone else made me look stupid hehe.

[fo3nix]

yea, you got it.