How does the energy stored in a capacitor change if after disconnecting the battery, the plates of a charged capacitor are moved farther?
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U=CV^2/2=εoA/d×V^2/2 ;
C=εoA/d
We can see that d is decreased then the U will increase.
Differentiate the U w. r. t.
d−∂U/∂d it is the change of energy stored if d is decreased
−∂U/∂d=εoAV^2/2×−1/d^2 ;
−∂U/∂d − is used because the we are decreasing d
So we get the −∂U/∂d
C=εoA/d
We can see that d is decreased then the U will increase.
Differentiate the U w. r. t.
d−∂U/∂d it is the change of energy stored if d is decreased
−∂U/∂d=εoAV^2/2×−1/d^2 ;
−∂U/∂d − is used because the we are decreasing d
So we get the −∂U/∂d
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