# Homework Help: In need of dire electrostatics help. Please check my work, provide insights, etc.

1. Feb 8, 2010

### Dmitri10

Here's a problem.
A house fly accumulates 3.0 (10)^-10 of positive charge as it flies through the air. What is the magnitude of the electric field at a location 2.0 cm from the fly?

Here's what I think.
I should use the equation E = kq/d^2. I am trying to find E.
k = 9.0 (10)^9
q = 3.0 (10)^-10 C
d = 0.02
So after plugging in the numbers... I arrive at the value of 6750 N/C.

However...
I thought that q in this case was supposed to be a test charge. And the only charge I have is most definitely the source charge. Am I wrong? Does this make a difference?

Any help would be greatly appreciated.

2. Feb 8, 2010

### fluidistic

Seems good to me. If they ask for the vector E, you should mention its direction, if the magnitude is asked, then I think you're right.

3. Feb 8, 2010

### Dmitri10

Okay, great. Thank you! I might have someone look over another question or two... so stay tuned! Haha

4. Feb 8, 2010

### Dmitri10

Okay, nevermind. I think I actually got all the rest of them!

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