# Work required?

1. Mar 9, 2016

### rgold

1. The problem statement, all variables and given/known data
two particles with charges 4e and -4e are fixed at the vertices of an equilateral triangle with sides of length a. If k=1/4 pi Ԑ what quantity of work is required to move a particle with a charge q from the other vertex to the center of the line joining the fixed charges?

2. Relevant equations
W = -delta U

3. The attempt at a solution
-(4kQq / a - 2kQq / a) = -2kQq / a => 2kQq / a
I know this is for when the charges are equal (both are Q) but Im not sure how to translate that into my problem...

2. Mar 9, 2016

### rgold

would it be (( 4*1/4 pi Ԑ *4) - (2*1/4 pi Ԑ *-4))/a?

3. Mar 9, 2016

### haruspex

No, it's for one charge of q and one of Q.

4. Mar 10, 2016

### rgold

I think I am just getting more confused and that I should start from the beginning... What is the best way to go about this problem?

5. Mar 10, 2016

### haruspex

What is the potential where the charge starts?

6. Mar 10, 2016

### rgold

kQq/r

7. Mar 10, 2016

### Qwertywerty

And the potential energy, at the time it starts?

You should also be using the brackets appropriately - 1/4πε0 is read as (1/4)*πε0.

8. Mar 10, 2016

### Qwertywerty

Also, which work is this?

9. Mar 10, 2016

### rgold

Wouldn't that be the work that I'm looking for?

10. Mar 10, 2016

### rgold

So would it be ((4*1/4πε)-(-4*1/4πε))/a?

11. Mar 10, 2016

### Qwertywerty

Is that the work done by the external force, or the electric force?
As hurspex pointed out, that is wrong. I was merely requesting you to write in a more, correct fashion. You will need to show your working.

12. Mar 10, 2016

### rgold

at first i thought i should be using (1/(4*πε0))*((q1q12)/r) is this correct? and should my answer have an 'a' is it?

13. Mar 10, 2016

### rgold

or do i need to look at it as a dipole moment?

14. Mar 10, 2016

### haruspex

I meant the total potential, due to the two fixed charges.

15. Mar 10, 2016