1. Impedance is the measure of the opposition that a circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current (AC) circuit

2. Resistance n Resistance affects flow of current by opposing the flow of electrons in a ckt

3. Inductance n Coil with wire wound around it n Opposes any change in current flow n It can not prevent the current from rising or falling but it will OPPOSE any rise or fall n Current in ac ckts is constantly changing any inductance in that ckt will oppose this change

4. Capacitance in A.C. Ckt n Made of 2 plates of conducting material n Constantly charged and discharged due to sine wave changes n The polarity of the voltage across the capacitor will be opposite of the supply voltage n Therefore it opposes the supply voltage and will result in a lower net voltage which cause the current to be lower

5. Capacitance in A.C CKT n Capacitance affects the current in the ckt by opposing a change in voltage n Capacitance cannot prevent the voltage from rising or falling but it will oppose the rise or fall

6. Summary A.C Resistance n Impedance measure in ohms (Z) n Inductive reactance in ohms (X L ) n Capacitance reactance in ohms (X C ) n Impedance includes u Resistance u Inductive Reactance u Capacitive Reactance u All measure in ohms

7. Summary A.C Resistance n Ohms law now becomes n Z is the total opposition to current flow in ac ckts measured in ohms