G485 - Capacitors and Exponential Decay

Question 1

Farad

Answer 1

One farad is a capacitance of one coulomb per volt

Question 2

Capacitance Equation

Answer 2

Q = CV

Question 3

Capacitance in Series Equation

Answer 3

1/Ct = 1/C1 + 1/C2 + 1/C3

Question 4

Capacitance in Parallel Equation

Answer 4

Ct = C1 + C2 + C3

Question 5

Capacitors in Series

Answer 5

Charge across each capacitor is the same as current is the same everywhere in a series circuit
Act as one big capacitor

Question 6

When are capacitors in parallel?

Answer 6

When all plates connect to other components directly

Question 7

What quantity is represented by the area under a potential difference against charge graph?

Answer 7

Energy stored by the capacitor

Question 8

What are the equations for the energy stored by a capacitor?

Answer 8

W = 1/2 QV = 1/2 CV²

Question 9

Time Constant

Answer 9

The time taken for the potential difference, current or charge across a capacitor to decrease to 1/e or 37% of the original value

Question 10

Time Constant Equation

Answer 10

t = RC

Question 11

Capacitance

Answer 11

The amount of charge stored per unit potential difference across a capacitor

Question 12

Applications for/of Capacitors

Answer 12

Energy store for:

• camera flash
• lasers used in nuclear fusion
• back up power for computers