Energy Stored by Capacitor Video Lessons

Concept

# Problem: A parallel-plate air capacitor has a capacitance of 920 pF. The charge on each plate is 3.90 μC. Part AWhat is the potential difference between the plates? Express your answer with the appropriate units. Part B If the charge is kept constant, what will be the potential difference between the plates if the separation is doubled? Express your answer with the appropriate units. Part C How much work is required to double the separation? Express your answer with the appropriate units (mJ)

###### FREE Expert Solution

The charge stored in a capacitor:

$\overline{){\mathbf{Q}}{\mathbf{=}}{\mathbf{C}}{\mathbf{V}}}$

Energy stored in a capacitor:

$\overline{){\mathbf{U}}{\mathbf{=}}\frac{\mathbf{1}}{\mathbf{2}}{{\mathbf{CV}}}^{{\mathbf{2}}}{\mathbf{=}}\frac{\mathbf{1}}{\mathbf{2}}{\mathbf{QV}}{\mathbf{=}}\frac{{\mathbf{Q}}^{\mathbf{2}}}{\mathbf{2}\mathbf{C}}}$

Capacitance of :

$\overline{){\mathbf{C}}{\mathbf{=}}\frac{{\mathbf{\epsilon }}_{\mathbf{0}}\mathbf{A}}{\mathbf{d}}}$

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###### Problem Details

A parallel-plate air capacitor has a capacitance of 920 pF. The charge on each plate is 3.90 μC.

Part A

What is the potential difference between the plates? Express your answer with the appropriate units.

Part B

If the charge is kept constant, what will be the potential difference between the plates if the separation is doubled? Express your answer with the appropriate units.

Part C

How much work is required to double the separation? Express your answer with the appropriate units (mJ)