1. Chapter 7 Parallel Circuits

2. Parallel Circuit Has two or more paths for electron flow. The electrons have choices to make as to where they go. Voltage Source Load

3. Voltage The voltage drop across each component is equal to the source voltage. E T = E 1 = E 2 = E 3 = E…= E N Total Voltage Voltage Drop # 2 Voltage Drop # 1

4. Current The total current in a parallel circuit is equal to the sum of the individual branch currents. I T = I 1 + I 2 + I 3 + I…+ I N Total Current Current at branch # 2 Current at branch # 1

5. Resistance Total resistance is always less than the smallest branch resistance. Methods of determining resistance in a parallel circuit: Product over the sum Reciprocal Equal resistances Graph method

6. Product Over The Sum Total Resistance R T = R 1 x R 2 R 1 + R 2 Can only be used when there are two resistances of unequal values

7. Reciprocal Method Can be used with three or more resistance values Total Resistance RTRT 1 = R3R3 1 R2R2 1 R1R1 1 …+++ RNRN 1

8. Equal Resistances Method Used when there are two or more resistances of equal value. The total resistance is equal to the value of one resistor divided by the total number of resistors in the parallel circuit R T = R N

9. Graph Method Use a bar chart; connect the top of the bars to the bottom of the other bar and estimate the value by where the lines cross. 20 15 10 5 0 R 1 = 20 R 2 = 15 R T ~ 8

10. Power Total Power consumed in a series circuit is equal to the source voltage multiplied by the circuit current. P T = P 1 + P 2 + P 3 … + P N

11. Ohm’s Law Can be applied to any individual component of a series circuit. If you know two values you can find the third. V = I x R I = V R R = V I

12. Troubleshooting Use totals to find missing branch values. Use branch totals to find missing totals. The voltage is the same everywhere. Current should flow through each branch, if it doesn’t something is wrong. (compare with calculations)