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First, the capacitance, 80 μf, is changed to farads by dividing 80 by 1,000,000, since 1 million microfarads is equal to 1 farad. This quotient equals 0.000080 farad. This is substituted in the equation: 

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## Impedance 

The total opposition to current flow in an AC circuit is known as impedance and is represented by the letter Z. The combined effects of resistance, inductive reactance, and capacitive reactance make up impedance (the total opposition to current flow in an AC circuit). In order to accurately calculate voltage and current in AC circuits, the effect of inductance and capacitance along with resistance must be considered. Impedance is measured in ohms. 

The rules and equations for DC circuits apply to AC circuits only when that circuit contains resistance alone and no inductance or capacitance. In both series and parallel circuits, if an AC circuit consists of resistance only, the value of the impedance is the same as the resistance, and Ohm’s Law for an AC circuit, I = E/Z, is exactly the same as for a DC circuit. Figure 9-22  illustrates a series circuit containing a heater element with 11 ohms resistance connected across a 110-volt source. To find how much current flows if 110 volts AC is applied, the following example is solved: 

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If there are two resistance values in parallel connected to an AC voltage, as seen in Figure 9-23,  impedance is equal to the total resistance of the circuit. Once again, the calculations would be handled the same as if it were a DC circuit and the following would apply: 

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Since this is a pure resistive circuit R$_{T}$ = Z (Resistance = Impedance) 

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To determine the current flow in the circuit use the equation: 

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Impedance is the total opposition to current flow in an AC circuit. If a circuit has inductance or capacitance, one must take into consideration resistance (R), inductive reactance (X$_{L}$), and/or capacitive reactance (X$_{C}$) to determine impedance (Z). In this case, Z does not equal R$_{T}$. Resistance and reactance (inductive or capacitive) cannot be added directly, but they 

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