# Hallow I found it very difficult to understand why the calculation

1. Sep 9, 2011

### Godwin Kessy

Hallow!! I found it very difficult to understand why the calculation

Hallow!! I found it very difficult to understand why the calculation for deducing the capacitance of the parallel plate capacitor differs from that of spherical and cylindrical capacitor...
In the sense that, the electric field in parallel plate capacitor is obtained as a resultant of the electric field due each capacitor..IE. The electric field is twice that produced by each plate... But for spherical and cylindrical capacitor the electric field used to obtain the potential difference across the surfaces and hence the capacitance, is as if only one surface is responsible for the electric field...
Now which is which...??
Personally am comfortable with using the electric field as the resultant of two fields from each surface.. Based on coulombs law of static electricity...

2. Sep 9, 2011

### Staff: Mentor

Re: Capacitors

Ask yourself: What's the field within the cavity of a hollow spherical conductor that carries a charge?

3. Sep 9, 2011

### Staff: Mentor

Re: Capacitors

My point is this: For all three configurations--parallel plate, cylindrical, and spherical--you can always find the field between the plates by adding the contribution from each plate. But in the latter two configurations, the outer plate contributes nothing.

4. Sep 15, 2011

### Godwin Kessy

Re: Capacitors

Now that's what confusing, see this, in all capacitors both charges, positive and negative are present, whats makes the other geometries different to the parallel plate?

5. Sep 15, 2011

### Staff: Mentor

Re: Capacitors

In the cylindrical and spherical capacitors, one conductor encloses the other. Not so in the parallel plate arrangement.