What is the relationship of charge and potential difference when charging a capacitor?

they are proportional

5 of 26

what are the 2 equations to calculate energy stored in a capacitor?

E=CV²/2 = QV/2

6 of 26

what is the area under a pd against charge graph?

energy stored by the capacitor

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what is the energy that is stored by the capacitor?

Electric potential energy

8 of 26

when discharging a capacitor, what happens to the current charge and pd and what is the term for this?

they all decrease when discharging and they decrease exponentially.

9 of 26

what is the percentage that the charge/current/pd drops down to after 1 time constant?

37%

10 of 26

What is the exponential equation to find charge when discharging a capacitor?

Q=Q e^(-t/RC)

11 of 26

what three quantities decrease exponentially when a capacitor is discharging in the form x=x e^(-t/RC)?

current, charge and pd

12 of 26

How many time constants does it take to discharge a capacitor? (pretty much)

5 (5RC)

13 of 26

What is the time constant?

RC - the time taken to discharge a capacitor to 0.37 of its initial value

14 of 26

what happens to voltage and what happens to current once a capacitor is fullt charged?

pd=source pd and current=0

15 of 26

What quantity has the same exponential graph when charging and discharging?

current

16 of 26

What does an exponential graph look like when discharging a capacitor?

Q against t graph:

17 of 26

what does an exponential graph when charging a capacitor look like (ignoring current)?

Q agaisnt t graph:

18 of 26

what is the equation for charge when charging a capacitor?

Q=Q (1-e^(-t/RC))

19 of 26

In the exponential equations, what is the value of e^-t/RC when t=0?

1

20 of 26

in the exponential equations, what is the value of e^-t/RC when t=infinity?

0

21 of 26

What is a dielectric?

electrically insulating materials that increase the ability of a parallel-plate capacitor to store charge.

22 of 26

What is relative permativity and what are the 3 different ways of calculating it?

Its the ratio of charge stored with the dielectric to the chaarge stored without the dielectric. =Q/Q =C/C =I/I

23 of 26

What is the capacitance of an 'empty' (no dielectric) capacitor c ?

(surface area of each plate x permitivity of free space)/spacing between the plates = A /d

24 of 26

What is the capacitance of a capacitor with a dielecrtic in it?

C=A /d

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What are the 3 ways of getting a larger capacitance?

- make surface area of each plate as large as possible - making plate spacing as small as possible - filling space between plates with dielectric with largest possible relative permitivity

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Other cards in this set

Card 2

Front

Define capacitance

Back

the charge stored per unit potential difference

Card 3

Front

That is the equation for capacitance

Back

Card 4

Front

what is the unit of capacitance?

Back

Card 5

Front

What is the relationship of charge and potential difference when charging a capacitor?

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