Electric field outside of conducting sphere.

[ramses07]

Homework Statement

A conducting sphere of radius 0.01 m has a charge of 1.0 × 10–9 C deposited on it. The magnitude of the electric field in N/C just outside the surface of the sphere is

Homework Equations

E=kq/r^2

EA=q/eo

The Attempt at a Solution

I tried the first equation and got 90000, but the answer is 900. I am racking my brains here trying to understand how to find the answer. Its seems simple enough, I am probably just missing a step, can anybody point to what I am doing wrong.

 

[Axiom17]

Could you show your calculations so far? Then can see where you're going wrong.

 

[hikaru1221]

Does the question mention the permittivity of the medium outside the sphere?

 

[Axiom17]

..also I got [itex]E=90000NC^{-1}[/itex] as well. Where did you get that the answer should be [itex]E=900NC^{-1}[/itex]? Also check those values you've been given are correct (but they seem OK).

 

[rdl]

It seems like you have the right equation, but you may have made a mistake in your calculation. The correct answer for the magnitude of the electric field just outside the surface of the conducting sphere is 900 N/C. To find this, you need to plug in the values of k (9 x 10^9 Nm^2/C^2), q (1.0 x 10^-9 C), and r (0.01 m) into the equation E = kq/r^2. This will give you a value of 900 N/C. It's possible that you may have made a calculation error, so double check your work to ensure you are getting the correct answer. Additionally, you could also use the second equation you listed, EA = q/eo, where eo is the permittivity of free space (8.85 x 10^-12 C^2/Nm^2). Plugging in the same values for q and r will also give you a result of 900 N/C. I hope this helps clarify the solution for you.