# Direction of electric field

1. Jul 23, 2007

### trah22

1. The problem statement, all variables and given/known data
a thin nonconducting rod is bent in a circular arc. Half is given a uniformly distributed postive charge and the other half uniformly negative. Draw the direction of the electric field at the center of the circle.

2. Relevant equations
E=Fe/qo, F=qE E=ke(q/r2)r

3. The attempt at a solution
Im not really sure what to apply here, a test particle is always postive, so if placed in the middle of the circle made by the bended rod it the electric field points to the negative side....

2. Jul 23, 2007

### Gokul43201

Staff Emeritus
That's correct. To make sure you've got this completely figured out try and draw the field lines everywhere (inside and ouside the ring).

3. Jul 23, 2007

### CaptainZappo

Electric field lines are drawn propagating outwards from a positive charge and in towards a negative charge. Using this knowledge, what can you determine about the electric field at the center of the said ring? Use symmetry arguments.

4. Jul 23, 2007

### trah22

doesnt there need to be a charge in the middle in the first place to relate the electric field to..?

Last edited: Jul 23, 2007
5. Jul 24, 2007

### CaptainZappo

The electric field is present regardless of whether or not a test charge is in place. The test charge serves the purpose of allowing one to manually probe the field and determine its strength at certain points.