Find capacitance and charge of two aluminum electrodes

[David23454]

Homework Statement

Two 3.0-cm-diameter aluminum electrodes are spaced 0.50 mm apart. The electrodes are connected to a 200 V battery. Find the capacitance of one of the spheres.

Homework Equations

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C=QV
C=ε₀A/d

The Attempt at a Solution

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I'm really not sure how to approach this problem. I tried solving the problem for the area of the sphere inserted into the formula, and when that turned out wrong, I then tried the volume, but the answers are not correct. I know that the formula C=ε₀A/d is for a parallel plate capacitor, so I'm pretty sure I can't use it as is because I'm dealing with spheres, but I don't know where to start.

 

[David23454]

does it have something to do with the electric field of a sphere E=Q/4πε₀?

 

[rude man]

If there are two spherical shells of practically equal radii R then you can argue that this is essentially a parallel-plate capacitor with plate area = 4πR² and separation 0.5 mm. In fact, the answer is very accurate since there are no fringing effects as in parallel-plate capacitors.

The problem is poorly worded so I'm guessing as to the two shells. Capacitance is for both shells, not just one ...