Question

How much energy, in picoJoules, is stored in a parallel plate capacitor connected to a 25.045 V battery? The plates at 18.655 cm x 18.655 cm, and separated by 7.686 mm with a thin sheet of polyethylene between the plates.

Answer 1

The energy can be found as follows:

`U=(1)/(2)CV^2`

where:

C = Capacitance

V = Voltage

We can find the Capacitance using the following formula:

`C=(\epsilon_pA)/(d)`

Where:

`\begin{gathered} \epsilon_p=Electric_{\text{ }}permittivity_{\text{ }}of_{\text{ }}polyethylene=2.25 \\ d=distance=7.686*10^(-3)m \\ A=Area=0.0348m^2 \end{gathered}`

So:

`C=10.1876F`

Therefore, the energy is:

`\begin{gathered} E=(1)/(2)(10.1876)(25.045^2) \\ E\approx3195.1J \end{gathered}`