Electric Potential Difference -- Conceptual Question

[anon1234]

Homework Statement

Potential difference (ΔV)measured by the student between the inner solid sphere and outer shell after putting a charge - 4Q is :

Relevant Equations

v = kq/r

I am able to get V1 = kq/a - 4kq/b
and V2 = kq/b + -4kq/b

For some reason the solution says it is V1-V2 as opposed to V2-V1.

Maybe has something to do with positive shell in the center and negative outer shell? I know the electric field goes from positive to negative, but I don't know how they relate.

 

[Delta2]

Please post a figure of the problem or describe it the best way you can. Your description of the problem is incomplete. Do we have a solid sphere of radius a and charge Q, surrounded by a shell of radius b and charge -4Q? Or do we have two shells? I really can't understand.

 

[anon1234]

Please post a figure of the problem or describe it the best way you can. Your description of the problem is incomplete. Do we have a solid sphere of radius a and charge Q, surrounded by a shell of radius b and charge -4Q? Or do we have two shells? I really can't understand.

It is 2 concentric shells. The first shell has radius a (charge Q), and the second shell has radius b (with charge -4Q).

 

[hutchphd]

How is the student measuring it? That might matter.

 

[anon1234]

How is the student measuring it? That might matter.

I hope this is ample info.

Both shells are made of insulating material, and the charges are distributed uniformly over its surface. Take the electric potential to be zero at an infinite distance from both shells. What is the magnitude of the potential difference between the surfaces
of the two shells?

 

[hutchphd]

What is the magnitude

This phrase implies a positive number...(?)

 

[anon1234]

This phrase implies a positive number...(?)

lol. ty!