# Physics

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A parallel-plate capacitor is constructed from two circular metal plates or radius R. The plates are separated by a distance of 1.2mm.
1. What radius must the plates have if the capacitance of this capacitor is 1.1 uF?
2. If the separation between the plates is increased, should the radius of the plates be increased or decreased to maintain a capacitance of 1.1 uF. Explain.
3. Find the radius of the plates that gives a capacitance of 1.1 uF for a plate separation of 3.4 mm.

I don't even know what formulas to use

• Physics -

All of these questions can be answered by using the same formula.

C = (epsilon)*A/d ,

where 'epsilon' is the permittivity of the dielectric between the plates.

If there is air or vacuum between the plates, use
epsilon0 = 8.85*10^-12 farads/meter

A is the plate are and d is the plate separation. Use meters.

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