Review21

# Review21 - Modified from College Physics 7th Ed Serway...

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Modified from College Physics , 7 th Ed., Serway, Faughn, and Vuille. For the quizzes and tests, you should know all the concepts and equations in this summary. Section 21.1: Resistors in an AC Circuit If an AC circuit consists of a generator and a resistor, the current in the circuit is in phase with the voltage, which means the current and voltage reach their maximum values at the same time. In discussions of voltages and currents in AC circuits, rms values of voltages are usually used. The rms values of currents and voltage ( I rms and V rms ), are related to the maximum values of these quantities ( I max and V max ) as follows: 2 , 2 max max V V I I rms rms = = [21.2] [21.3] The rms voltage across a resistor is related to the rms current in the resistor by Ohm's law : R I V rms rms = [21.4] Section 21.2: Capacitors in an AC Circuit If an AC circuit consists of a generator and a capacitor, the voltage lags behind the current by 90°. This means that the voltage reaches its maximum value one-quarter of a period after the current reaches its maximum value. (Positive voltage opposes current flow, as in a resistor.)

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Review21 - Modified from College Physics 7th Ed Serway...

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