Question

A parallel-plate capacitor has plates of area 0.16 m2 and a separation of 1.20 cm. A
battery charges the plates to a potential difference of 180 V and is then
disconnected. A dielectric slab of thickness 0.4 cm and dielectric constant K=3 is
then placed symmetrically between the plates.
a) What is the capacitance before the slab is inserted?
b) What is the capacitance with the slab in place?
c) What is the free charge q before the slab is inserted?
d) What is the free charge q after the slab is inserted?
e) What is the magnitude of the electric field in the space between the plates
and dielectric?
f) What is the magnitude of the electric field in the dielectric itself?
g) With the slab in place, what is the potential difference across the plates?
h) How much external work is involved in the process of inserting the slab?
i) What is the minimum dielectric strength that the dielectric must withstand
so that it will not break when it is placed in the capacitor?
j) Assume that I repeat the process (charge my initial capacitor to the same
battery, then remove the battery) but then instead of introducing a slab of
dielectric I introduce an identically shaped slab made out of solid copper.
How will any of the answers to questions b), d), e), f), g) and h) ?

Answer 1