Capacitors

Question 1

Define capacitance

Answer 1

Charge stored per unit potential difference across the capacitor

Question 2

What is the relative permittivity (dielectric constant)?

Answer 2

The ratio of the charged stored when the dielectric is between the plates to the charge stored when the dielectric is not present.

Question 3

What is the half time of the capacitor?

Answer 3

0.69RC

Question 4

Describe the graphs for current during charging and discharging

Answer 4

Both show exponential decay

Question 5

Describe the motion of a simple polar molecule in an electric field

Answer 5

Polar molecules have a positive end and a negative end. When placed in a capacitor, the molecules align, and the positive ends are attracted to the negative plate, and the negative ends are attracted to the positive plate.

Question 6

Explain why energy is stored in a capacitor when it is charged

Answer 6

Energy is stored in a capacitor during charging because work is done to move charges against the electric field between the capacitor plates. This work is stored as potential energy in the electric field between the plates.