SERIES-PARALLEL COMBINATION CIRCUITS USES A SERIES OF EQUIVALENT RESISTANCES TO SOLVE FOR THE TOTAL RESISTANCE IN A CIRCUIT
Always start with resistors farthest from the voltage source. Look over circuit to see how resistors are placed in the circuit. R2 and R3 are in parallel with each other. This combination is in series with R1
EX: Two 12Ω resistors are connected in parallel and placed in series with a 6Ω resistor. The total voltage supplied to the circuit is 120V. Draw and label the circuit. = 6Ω =12Ω VT=120V =12Ω
b) Find the total resistance and total current in the circuit. RT = R1 + Req RT = 6Ω + 6Ω RT = 12Ω RT = VT/ IT 12Ω = 120V/ IT IT = 10 Amps 1/Req= 1/12Ω + 1/12Ω 1/Req = 2/12 Req = 6Ω R1=6Ω Req= 6Ω
c) Find V1 V3 and I3. R1= V1 / I1 V2 =V3 = VT – V1 6Ω = V1/ 10 Amps V2 =V3 = 120V-60V V1 = 60V V2 =V3 = 60V R3 = V3/ I3 12Ω = 60V/ I3 I3 = 5 Amps
I1=10 Amps V1=60V =6Ω IT=10Amps I3=5A I2=5Amps VT=120V =12Ω = V2 = 60V 12Ω V3=60V
4.0 15 10 1.0 V= 9V Find the total resistance of the circuit. If the battery is 9.0V, what is the total current in the circuit? What is the current in R2 and R5?