# Need help with LC Circuit calculate the time

#### Tessa R

Joined Jun 22, 2019
1
The question asks: In the circuit, the capacitor is fully charged when switch S is closed. Calculate the time needed for the potential energy stored by the circuit to be equally distributed between the capacitor and inductor. The capacitance is C=20.0MF and the inductance is L=65.0 H.

My attempt at this problem was to use the equation. 1/(LC)^sqroot and then taken that value solve for time using w=2pif
However since it is asking for potential energy do I have to use Qcos(wt)? I am just confused at how I could use the other potential energy equations I know without having the charge.

Would anyone be able to point me in the right direction of equations to use/how to set up the problem?

Thank you

#### WBahn

Joined Mar 31, 2012
30,045
In what circuit?

Do you really mean 20 million farads?

Assuming that the two components are simply connected together in a lossless tank circuit once the switch is closed, what's the equation for the current and the voltage as a function of time? You know it is a sinusoid and you know the frequency and you know the initial conditions.