Section One - Capacitance

Question 1

What are capacitors?

Answer 1

Electrical component that can store charge.

Question 2

What is the composition of a capacitor?

Answer 2

Two conducting plates, usually separated by a dialectric

Question 3

What is a dialectric and why is it useful?

Answer 3

An insulating material, to stop charge from flowing between plates of the capacitor

Question 4

Unit of capacitance?

Answer 4

Farad.

Question 5

Equation for capacitance?

Answer 5

Q=CV

Question 6

Capacitance in parallel circuits and series circuits?

Answer 6

Parallel: Ctotal= C1+ C2

Series 1/Ctotal=1/C1 + 1/C2

Question 7

Equation for energy stored by the capacitor?

Answer 7

W = 1/2 QV

Question 8

Why are capacitors useful? + uses

Answer 8

Discharge quicker than batteries and can be used for flash photography or backups to power supplies

Question 9

Equation for discharging a capacitor?

Answer 9

Q=Qoe^-t/CR

Can also use I or V

Question 10

Equation for charging a capacitor?

Answer 10

Q=Qo(1-e^-t/CR)

Or I / V

Question 11

Factors affecting time to charge or discharge capacitors?

And why

Answer 11

The capacitance - affects the amount of charge that can be transferred at a given voltage

Resistance - affects the current

Question 12

What is the time constant?

Answer 12

Time take for capacitor to discharge by 63%

100-37% charge level

Question 13

Equation for time constant?

Answer 13

T(tau) = CR

Question 14

Charging a capacitor (time constant)?

Answer 14

Time take to charge by 63 %

Question 15

How does resistance of resistor in series with the capacitor affect the time take to charge?

Answer 15

Longer if higher resistance.