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Page 12

| Figure 1-12 Effect of capacitance on voltage and current in a conductor (not drawn to scale). |

| area of the conductors exposed to each other, the distance between them, the kind of insulating material between them, and the voltage (and current) in the conductors. Like the inductance in a circuit, the current set up in a conductor because of this capacitive effect will tend to cause the resultant current to be displaced from the voltage wave (Fig. 1-12). The obstructive effect of this capacitance phenomenon between conductors is called capacitive reactance, and is also measured in ohms. |

| Impedance |

| The total obstruction to the flow of current in an ac circuit may, therefore, be caused by resistance, inductance, and capacitance or more generally, resistance and reactance. This total obstruction, which impedes the flow of electricity, is called impedance (usually denoted by the letter Z). In ac circuits, then, Ohm's Law becomes |

| where I is the current, E the voltage, and Z the impedance. |

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