Flashcards
Capacitors Quiz
Cards in this deck (15)
- 1Define CapacitanceThe amount of charge stored per volt
- 2C = Q / VCapacitance (F) = Charge (C) / potential difference (V)
- 3The energy stored by a capacitor is equal tothe work done by the battery
- 4area under a p.d. against charge stored graph = ?Energy Stored
- 5The p.d. across the capacitor is ? to the charge stored on itproportional
= straight line graph through the origin - 6Equation for energy stored by a capacitor (from the graph) =W =1/2/ QV
- 7Derive W = 1/2/ CV^2Q = CV
W = 1/2 QV
W = 1/2 Cv^2 - 8Derive W = Q^2 / 2CV = Q/ C
W = 1/2 QV
W = 1/2 Q x Q/C (1 into 2)
W = 1/2 Q^2 /C
W = Q^2 / 2C - 9Charging A CapacitorElectrons flow onto the plate connected to the negative terminal - a negative charge builds up
The negative charge repels electrons off of the plate connected to the positive terminal, making it positively charged
Equal but opposite charge builds on the plates causing a p.d. between the plates
Initially the current is high, but as charge builds up on the plates electrostatic repulsion makes it harder for more electrons to be deposited. When the capacitor and battery have the same p.d. the current = 0. (Fully Charged) - 10Discharging A CapacitorWhen a charged capacitor is connected across a resistor the p.d. drives a current through the circuit
Current flows in the opposite direction from the charging current
when p.d. and the current = 0 the capacitor is fully discharged - 11The time taken to charge or discharge a capacitor depends on:The capacitance of the capacitor (affects the amount of charge that can be transferred at a given voltage)
The resistance of the circuit (affects the current) - 12time to charge a capacitor =t = RC
- 13The charge on a capacitor decreases . . .exponentially
- 14Discharging capacitor equationQ = Q0 e ^-t/RC
- 15T constant for exponential discharging on a graph =1/e because Q/Q0
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- a level Physics (Unit 4 - Section 2: Electric & Magnetic Fields) Flashcards on Capacitors Quiz , created by 2008schulz on 31/05/2015.
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