The plates of a capacitor have an area A and each plate contains a charge magnit

Question

The plates of a capacitor have an area A and each plate contains a charge magnitude of Q. The plate separation is d. In terms of these symbols and any others that are required,

a)     What is the charge density on the plates (magnitude)?

b)    What is the Electric Field between the plates?

c)     What is the potential difference between the plates?

d)    What is the capacitance of this device?

e)     The owner of the capacitor decides to pull the plates a little further apart.

                                                                   i.            What force does she have to apply to accomplish this?

                                                                 ii.            How much work does she do if she wants to double the spacing between these plates?

                                                              iii.            Her significant other now enters the room and says that the spacing is now right but she needs to increase the capacitance of the device by 50% by putting some insulating material into the gap. Suggest the appropriate material if possible or if it can’t be done, explain why.

Explanation / Answer

Here,

part A)

charge density on plates = charge/area of plates

charge density on plates = Q/A

part b)

electric field between plates = charge density/0

electric field between plates = Q/(A *0)

part c)

electric potential between the plates = electric field * seperation

electric potential between the plates = Q/(A *0) * d

electric potential between the plates = Q* d/(A *0)

part d)

for a parallel plate capacitor

capacitance = A *0/d

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