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## Homework Statement

The effective voltage in an LC circuit is 200V while the capacitance of the capacitor in the circuit is 20pF. What is the maximum capacitor energy?

## Homework Equations

We = CU^2/2

Uefective = U / sqrt(2)

## The Attempt at a Solution

Well it seems a fairly simple problem. It solves by just calculating the energy by putting the given information in the energy equation above, and the answer is supposed to be 4*10^-7 J.

However, this is not the way I solved it. As it states in the problem, the

__effective voltage__of the system is supposed to be 200V, as there is AC going through it. So shouldnt we calculate the peak voltage first, which is 200*sqrt(2) and use it to calculate the

__maximum__energy of the capacitor, which would be when the capacitor is fully charged and there is no current goingh through the system? By doing this we get the answer to be 8*10^-7 J.

So where does my logic fail?

Thanks in advance,

fawk3s