# 5.2.1 CAPACITORS

What is

Define capacitance
charge per unit potential; difference
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coulomb per init volt
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What is a capacitor?
two metal plates separate day an insulator/ when connected to a source of emf charges on plates are equal and opposite/ stores charge
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Describe capacitors in series
1/c1 + 1/c2 .... / voltage is split between components/ charge stored is the same
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Describe capacitors in parallel
c1 + c2/ voltage across is the same / charge is split between components
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Describe the work done by a capacitor
work is done when charging and discharging/ work done against repulsive forces/ V vs C graph area under line is W
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Describe the discharge of a capacitor through a resistor
charge will decrease exponentially wrt time/ as Q=VC and V=IR both voltage and current will decrease in the same way
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What is the time constant of a circuit?
time taken for the charge to have decreased to 1/e of the original (fall by 37%)
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Describe the constant-ratio property of exponential decays
'constant half life' time taken for Q to half is always the same
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What does the time taken for a capacitor to charge/discharge depend on?
C - amount of charge that can be transferred per unit V/ Resistance affects the current
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How long does it take for a capacitor to completely charge/recharge?
5CR
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What are the uses of capacitors?
takes only a few seconds to charge then can be discharged rapidly - flash bulbs/ back up batteries for computers etc.
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## Other cards in this set

### Card 2

#### Back

coulomb per init volt

### Card 3

#### Front

What is a capacitor?

### Card 4

#### Front

Describe capacitors in series

### Card 5

#### Front

Describe capacitors in parallel