1. Resistance in Series and Parallel

2. Series Equivalent Resistance: Rt = R1 + R2 + R3
equivalent resistance of loads in series found by adding up the resistance of the individual loads
Rt = R1 + R2 + R3
Current decreases as more loads are added
Voltage in each load decreases as more loads are added so individual resistance can stay constant.

3. Parallel Equivalent Resistance 1/Rt = 1/R1 + 1/ R2 + 1/R3
equivalent resistance of loads in parallel is lower than the resistance of any of the individual loads. It is calculated as:
1/Rt = 1/R1 + 1/ R2 + 1/R3
Voltage of each load is the same as the sources
Current stays constant

4. Eg) If 3 resistors are connected in a parallel circuit, determine the total resistance. Resistor 1 is 2 ohms, resistor 2 is 4 ohms and resistor 3 is 6 ohms.
1/Rt = 1/R1 + 1/ R2 + 1/R3
1/Rt = 1 /2 + ¼ + 1/6
1/Rt = 6/ /12 + 2/12
1/Rt = 11/12
Rt = 12/11
Rt = 1.09ohms