where:

I = current in amperes |

V = voltage in volts |

Z = impedance in ohms |

W = VI(pf) |

where:

W | = power in watts |

pf | = power factor |

The power factor is the ratio of actual power in a circuit measured in watts to the apparent power in volt-amperes. In a circuit with only resistive loads, such as incandescent lights or electric heating elements, impedance equals resistance, and the power factor is 1.0. Therefore, W = VI.

Find the current in a 120 volt circuit serving nine 150 watt downlights. From the formula just given,

Since the power factor is 1, then

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