# Easy Electric Potentional Problem

1. Sep 12, 2009

### exitwound

1. The problem statement, all variables and given/known data

The electric potential difference between the ground and a cloud in a particular thunderstorm is 1.5E9 V. What is the magnitude of the change in the electric potential energy of an electron that moves between the ground and the cloud?

_____ GeV

2. Relevant equations

U\q=V

3. The attempt at a solution

This should be simple.

U=qV
U=(1.6e-19)(1.5 GV)
U=2.4e-19 GeV

Why is this not right?

2. Sep 13, 2009

### exitwound

Anyone? Still can't figure it out.

3. Sep 13, 2009

### exitwound

NO one at all????

4. Sep 13, 2009

### Redbelly98

Staff Emeritus
What are the units on the 1.6e-19? Include the units in the calculation.

5. Sep 13, 2009

### exitwound

Coulombs. I'm not following.

6. Sep 13, 2009

### Redbelly98

Staff Emeritus
Correct.

That would make the units in your answer Coulombs*V, and not eV. You'll have to convert to eV (or GeV).

7. Sep 13, 2009

### exitwound

So, ... what, I divide by 1.6x10^-19?

U=2.4e-19 / 1.6e-19 = 1.5 GeV

There are too many stupid units in electromagnetism! This is driving me crazy.

8. Sep 14, 2009

### Redbelly98

Staff Emeritus
Yes. (Or don't multiply by 1.6x10^-19 in the first place.)

Yes, you got it.

You get used to it after awhile.

By the way, if you use elementary charge units instead of Coulombs here, it's simpler:

An electron has -1.00 elementary charges or -1.00 e of charge, so

U = q V
= (1.00 e) (1.5e9 V)
= ___ eV
= ___ GeV​