# Homework Help: Two dipoles on an axis. There is one point where the E field vanishes.

1. Dec 11, 2012

### _Chemicals_

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

2. Relevant equations
None given. Pondering:

E=(1/(2(pi)εnaught))(σ/z^3)
p=qd
U=-p dotprod E

3. The attempt at a solution
We have attempted many variations of the above equations to try and find the answer. We are just seeking a point in the right direction as we are currently reviewing for a final. Any help is appreciated, thank you!

2. Dec 11, 2012

### ehild

The relevant equation is given in the problem text:
. You have two dipoles, one of magnitude p1=27 Cm, the other p2=1Cm at distance L from each other. What is their resultant field at distance x from the bigger one?

ehild

3. Dec 12, 2012

### _Chemicals_

We're still confused :(

4. Dec 12, 2012

### Simon Bridge

If you put the origin at the position of the bigger dipole - can you write the equation for the combined field at position x?

5. Dec 12, 2012

### ehild

What confuses you?

You certainly know what a dipole is: you can imagine it like a compass, but it is electric instead of being magnetic. There is an electric field around it, as if it were a pair of charge, a positive and a negative, some small distance apart. You also know that the electric field strength is the force exerted on unit positive charge: it has direction. Place a positive charge at distance x to the right from the 27Cm dipole. What is the direction of the force it exerts on the charge? What is the direction of the force the other dipole exerts?

ehild

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