Homework Help: Electric field strength

1. Jun 12, 2014

Burger

Physics Problem , please help I'm writing a test tomorrow and want to know if I'm right.
The Question :

Two point charges Q1 and Q2 are spaced 3m apart.

Q1's charge = 14C
Q2's charge = +20 C

*Q1 -------(3meters)------- *Q2 ----(2meters)---- *P

Calculate the net electric field at point P, 2m right from where Q2 is situated?

My Calculations :

Q1 on P = -5.04 x10^9
Q2 on P = 4.5 x10^10

Final answer = Net : 3.996x10^10

Formula used:

E = (k*Q)/r^2

2. Jun 12, 2014

TSny

Hello, Burger. Welcome to PF!

Did you forget to include the sign of Q1 when you stated Q1 = 14 C?

Just to be sure that you have a full understanding, what is the interpretation of the negative sign for your answer for the electric field of Q1 at P?

Finally, electric field is a vector. So, it has a magnitude and a direction. Therefore, your final answer for the field at P should include both a magnitude and a direction. The direction should be clearly stated and not left to the reader to interpret.

Otherwise, your numbers look good! (You're getting a very large answer because a Coulomb is a huge amount of static charge.)

3. Jun 12, 2014

Burger

Q1's charge = -14 C

Thanks for the help! Will ace the Test hopefully. I must just remember to include the direction the N•C^-1

4. Jun 12, 2014

TSny

OK. Good luck with the test!