The capacitor has a cross-sectional area A and a distance between plates of 10 mm. A battery with voltage of 30 volts is connected across the plates of the capacitor. There is nothing between the plates of the capacitor. A dotted line AB is 1 mm from the top plate and a dotted line CD is 8 mm from the top plate. The lines are 10 mm long and are centered on the plates.
a) What is the potential at B
b) What is the potential at C
c) if the voltage of the battery was doubled, what is the potential at A
d) if the voltage of the battery was doubled, what is the potential at D