What is the Relationship Between Electric Field and Potential?

[shirel]

Hi,

I don't understand why dV/dr=-E

As far as I know:
V=kq/r
E=Kq/(r^2)
so V/r becomes to be E and not -E.

 

[Doc Al]

V=kq/r

What's dV/dr for that potential? Compare that to E.

 

[shirel]

ohh I should derivate the function! thank you :)