Damn units and surface charge density.

[frasifrasi]

Ok, the question asks:

An electron close to a large, flat sheet of charge is repelled from the sheet with a 2.1×10^−12 {N} force.

Q. find the surface charge density on the sheet in C/m^2

What i did was use the formula F = qe with 2.1e-12 for the force and 6.1e-19 for the charge of an electron. This gives me E,which I used in the formula E = (surface charge density)/2epsilon_0.

Plugging everything in (epsilon_0 = 8.85e-12), I get 2.32e-42, but It says it is wrong.

Does anyone know why?

Thanks.

 

[Redbelly98]

Your formulas are correct, so there's a calculation error somewhere.

2.32e-42 C/m^2 is less than 1 electron per square kilometer!

 

[frasifrasi]

I keep getting it wrong!

Can anyone verify the above is correct?

Much appreciated.

 

[Redbelly98]

Can anyone verify the above is correct?

The above is not correct. It's 2.32 x (A different power of 10 then -42)

Can you show some intermediate results? What did you get for the E-field?