Capacitors

Question 1

What is a capacitor?

Answer 1

An electrical component that stores charge on two parallel separated plates.

Question 2

Why can’t current flow through a capacitor?

Answer 2

The 2 plates of a capacitor are separated by an insulator such as air.

Question 3

Define capacitance

Answer 3

The charge stored per unit potential difference.

Question 4

Define Farad

Answer 4

One Coulomb per Volt

Question 5

How does a capacitor gain a store of energy?

Answer 5

Due to work done to move a charge Q onto the plates.

Question 6

What does x represent in the equation X = X0 e^–t/RC ?

Answer 6

Q, V or I

Question 7

Define time constant

Answer 7

The time taken for the charge (or V or I) to reach e^-1 of any initial value.

Question 8

What do the letters represent in the formula C = ε0εrA / d = εA / d ?

Answer 8

C - capacitance
εr - relative permissive of the material (insulator)
A - area of each plate
ε0 x εr = ε
εr > 1

Question 9

What type of relationship is between C and V?

Answer 9

C is inversely proportional to V
The largest C gets the smallest V.

Question 10

What is the formula for capacitors in series?

Answer 10

1/C = 1/C1 + 1/C2

Question 11

What is the formula for capacitors in parallel?

Answer 11

C = C1 + C2