# Electric Field

1. Sep 11, 2008

### Kathi201

Three positive and equal charges Q1, Q2, and Q3 are at the corners of an equilateral triangle. Point P is at the midpoint of the line between Q1 and Q3 (the middle of the bottom of the equilateral triangle). The electric field at P is
A.zero
b. not zero and directed along the line from P to Q3
c.not zero and is directed along the line from P to Q2
d. not zero and is directed along the line from Q1 to Q2
E.none of these are correct

My thinking is that the answer is zero. I know that the electric field points away from positive charges so if Q1 and Q3 are at the bottom of the equilateral triangle the P is in the middle they are going to direct the opposite way and cancel each other out.

Anybody know if this is correct or have a reason why another answer would be correct?

2. Sep 12, 2008

### alphysicist

Hi Kathi201,

You're right that the electric field from Q1 and Q3 are going to cancel. But what about the field at P from Q2?

3. Sep 12, 2008

### Kathi201

Oh Ok thank you I forgot about Charge Q2. So the electric field at P is going to be directed along the line from P to Q2.