# A Level Physics-Electric Fields help

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#1
For (b) of this question a method in the mark scheme states V = Ex (for a point charge) where x is distance. Can anyone explain this equation?
Last edited by cruduxcruo9; 8 months ago
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8 months ago
#2
(Original post by cruduxcruo9)
For (b) of this question a method in the mark scheme states V = Ex (for a point charge) where x is distance. Can anyone explain this equation?
I can understand your dilemma. This is the grey area where a full Maths analysis is needed. BUT as a shortcut ...(*x is a distance) because
Potential Difference = (Force / Charge) x Distance
But this formula only works when the Force on the Charge is Constant and the Electric Field is Constant (NOT TRUE for point charges)
Clearly, thus is not the case so we have to revert to calculus and say that
THE AREA Under the Force - Distance graph is the Energy or Work Done.
But you have a graph of Electric Field v Distance so you need to make a factor adjustment of this. Force = Electric Field x Charge
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8 months ago
#3
(Original post by cruduxcruo9)
For (b) of this question a method in the mark scheme states V = Ex (for a point charge) where x is distance. Can anyone explain this equation?

The equation or expression V = Ex is actually

in the disguise.

If a point charge Q is responsible for the electric field, then the magnitude of electric field strength of the point charge Q is

and the electric potential due to the point charge Q is

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