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## Homework Statement

How do I calculate the Field Strength if I know the Potential?

## Homework Equations

E = -[itex]\nabla[/itex]V

V = Electric Potential

E = Electric Field Strength

## The Attempt at a Solution

There's a problem in which I calculated the Potential, it's constant however. So according to the equation that means that the Field Strength is 0?

In the solution they calculated them individually, and the Field Strength wasn't equal to 0.

In the problem, the "body" is a ball and I calculated the potential with respect to origo (centrum of the ball) and so in my answer all I got was in terms of the largest radius (constant) and the volume charge distribution. My potential is correct too, according to the solution, and is a constant.

I think they got that the Field Strength is equal to the potential (in magnitude) in the direction of the negative z-axis.

So how do I get the Field Strength by using the Potential I calculated?