# Capacitors Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Define capacitance.

A

The amount of charge stored per volt.

2
Q

A

1 farad is the capacitance when 1C is stored over a potential difference of 1V.

3
Q

State the equation for the total capacitance of two or more capacitors in series.

A

total capacitance = (1/C1 + 1/C2…)^(-1)

4
Q

State the equation for the total capacitance of two or more capacitors in parallel.

A

total capacitance = C1 + C2…

5
Q

What does the area under a potential difference against charge graph represent?

A

The energy stored by a capacitor.

6
Q

Describe the graph that occurs for potential difference/charge/current against time for a discharging capacitor.

A

These graphs are all the same, and show exponential decay.

7
Q

Define time constant.

A

The time constant is the time taken for current, charged stored, or potential difference across to fall to about 1/e (37%) of it’s initial value.

8
Q

Is we measure an amount that shows exponential decay at regular intervals, how can we show that this is exponential decay?

A

The measurements next to each other will show a constant ratio. eg. A2/A1 = A1/A0

9
Q

Describe how a capacitor is used in flash photography.

A

Charge from a capacitor flows through xenon gas, emitting a bright light. The capacitor discharges really quickly to give a short pulse of high current that produces a brief flash of light.

10
Q

Give an example of a use of a capacitor.

A

In flash photography, nuclear fusion, and as a back-up power supply.

11
Q

How are capacitors used in nuclear fusion?

A

The capacitors control the lasers that give the reaction its energy. They release a huge charge in a fraction of a second to maximise the amount of energy in the laser-light.

12
Q

How are capacitors used in back-up power supplies for computers?

A

A large capacitor will release charge slowly if the power supply fails. This gives you time to save a retrieve data if needed.