1. How to Calculate Total Circuit Current in a Series Circuit ?

2. Review: Combination of Resistors The simplest resistor combination is two identical resistors in series,as shown in Figure B–8(a). The current is the same in the two resistors In general, the resistance of any number of resistors in series is the sum of the individual resistances: R series = R1 R1 + R2 R2 +  + RnRn

3. Review: Parallel Resistors or, = 1

4. First: Simplify a Series Circuit RS RS = R1 R1 + R2 R2 + R3R3

5. Simplifying a Series Circuit RS RS = R1 R1 + R2 R2 + R3R3 = 10 + + 20 = 40 

6. Then Calculate Total Current using Ohm’s Law IS IS = VS VS / RSRS = 20V / 40  = 0.5 A

7. Calculate Voltage Drops across each Resistor using Ohm’s Law V R1 = IS IS x R1R1 = 0.5 A x 10  = 5 V V R2 = IS IS x R2R2 = 0.5 A x 10  = 5 V V R3 = IS IS x R3R3 = 0.5 A x 20  = 10 V Kirchhoff’s Voltage Law: VS VS = V R1 + V R2 + V R3 in a loop 20 = 5 + 5 + 10

8. Simplify a Series Circuit