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Electric Circuits. AP Physics. Capacitors in Series. Capacitors in series share the same charge magnitude. Capacitors in Series. C 1. C 2. C 3. Capacitors in Series.
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Electric Circuits AP Physics
Capacitors in Series Capacitors in series share the same charge magnitude. Capacitors in Series C1 C2 C3
Capacitors in Series For capacitors connected in series the reciprocal of the equivalent capacitance is equal to the sum of the reciprocals of the individual capacitances: Capacitors in Series C1 If C1 = 6 μF, C2 = 2 μF, and C3 = 3 μF, what is the equivalent capacitance Ceq of the circuit? C2 C3 Notice that the equivalent capacitance is less than any of the individual capacitances. This is true any time capacitors are connected in series.
Capacitors in Parallel Parallel Circuit C2 C1 C3 Capacitors in parallel share the same potential difference.
Capacitors in Parallel Parallel Circuit If C1 = 6 μF, C2 = 2 μF, and C3 = 3 μF, what is the equivalent capacitance Ceq of the circuit? C2 C1 C3 The equivalent capacitance of capacitors connected in parallel is always more than the capacitance of any one capacitor. For capacitors connected in parallel the equivalent capacitance of the system is the sum of the capacitances of all the capacitors:
Capacitor Circuit 30 µF 180 V 90 µF 60 µF Find the charge stored and the voltage across each capacitor in the following circuit.
Capacitor Circuit 30 µF 180 V 90 µF 60 µF Find the energy stored in the circuit at equilibrium.
Capacitor Circuit (Alt. Method) 180 V 30 µF 180 V 90 µF 60 µF Find the energy stored in the circuit at equilibrium. Find the equivalent capacitance.
Burning Questions Why do the charges flow? When can they flow? If the charges are always flowing from high potential to low potential how do they get at a higher potential to begin with?
Electromotive Force (emf) Emf is not a force. It is an “energy per unit charge” quantity (just like potential). Symbol: Units are _____________________________________ What supplies the emf? Batteries, generators, power supplies These objects are like a water pump in a continuously flowing fountain
Ideal or not? I ε = Vtot R I ε R Vtot r Ideal sources of emf have no internal resistance. Most sources of emf are not ideal and have some internal resistance r.
Dying Battery I Vtot ε R r As a flashlight battery ages, its emf stays approximately constant, but its internal resistance increases. A fresh battery has an emf of 1.5 V and negligible internal resistance. When the battery needs replacement, its emf is still 1.5 V, but its internal resistance has increased to 1000 Ω. If this old battery is supplying 1.0 mA to a lightbulb, what is its terminal voltage?