Solving a Voltage Problem - Q, E Field, E Potential

[bodensee9]

Can someone see what I am doing wrong here?

A charge of q = +10-7 C is uniformly distributed on a spherical shell of radius 15 cm.

(a) what is the E field just outside the shell.

Isn't the E field given by k*Q/R^2 where Q is total charge (10e-7 C) and R, since it's immediately outside, .15m? So wouldn't I get 399.555 kV?

(b)what's the magnitude of potential just inside and outside of the shell, and at the center?

Isn't the E potential just k*Q/R, where R is the radius of the shell. And it's the same value everywhere inside because since the field is 0 so the potential must be constant. So wouldn't the answer be (8.99e9)*10e-7/.15 = 59933.333 V?

Thanks.

 

[Defennder]

(a) what is the E field just outside the shell.

Isn't the E field given by k*Q/R^2 where Q is total charge (10e-7 C) and R, since it's immediately outside, .15m? So wouldn't I get 399.555 kV? p

Looks ok, but check your units.

(b)what's the magnitude of potential just inside and outside of the shell, and at the center?

Isn't the E potential just k*Q/R, where R is the radius of the shell. And it's the same value everywhere inside because since the field is 0 so the potential must be constant. So wouldn't the answer be (8.99e9)*10e-7/.15 = 59933.333 V?

Looks ok as well, if you substituted and computed the numbers properly.