Chapter 29 Power,power factor and power factor correction

29.1 Power in a.c. circuits

Earlier, in Chapter 21, we showed how the power in a d.c. circuit is simply the product of the applied voltage and current. However, there is an added complication in an a.c. circuit where the voltage and current do not rise and fall together (i.e. when they are not in phase). In this case we need to consider the instantaneous curve of power over a complete cycle of the supply in order to determine the relationship between voltage, current and power in the circuit. We will start by considering how the power varies over a complete cycle of the supply in the ...

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