Capacitors (M6)

Question 1

Total capacitance in parallel

Answer 1

C = C1 + C2 + …

Question 2

Potential difference of capacitors in parallel

Answer 2

P.d. across each is the same

Question 3

Charge of capacitors in parallel

Answer 3

Charge is conserved
Q = Q1 + Q2 + …

Question 4

Total capacitance in series

Answer 4

1/C = 1/C1 + 1/C2 + …

Question 5

P.d. across capacitors in series

Answer 5

Kirchhoff’s second law
V = V1 + V2 + …

Question 6

Charge of capacitors in series

Answer 6

Charge in each is the same

Question 7

Uses of capacitors

Answer 7

Camera flash - release large amount of stored energy very quickly

Provide backup power for computers briefly

Smoothing the output voltage from an AC generator

Question 8

Capacitor charging (electrons)

Answer 8

Electrons flow for a very short time.
They are removed from plate A and deposited onto plate B. A is positive, B is negative.
Charge is equal and opposite, net charge is 0.

Question 9

Investigating circuits

Answer 9

Power supply, switch, safety resistor, ammeter in series.
Capacitors in different layouts, each with a voltmeter in parallel.
Ammeter will briefly register a current but then settle at 0.

Question 10

Discharging current time graph

Answer 10

Slope down

Question 11

Discharging voltage time graph

Answer 11

Slope down

Question 12

Discharging charge time graph

Answer 12

Slope down

Question 13

Charging current time graph

Answer 13

Slope down

Question 14

Charging charge time graph

Answer 14

Slope up

Question 15

Charging voltage time graph

Answer 15

Slope up

Question 16

Capacitance of a parallel plate

Answer 16

C = EA/d
E = permittivity of the insulator (dielectric)
A = area of overlap
d = separation