1. Circuits and Circuit Elements
Resistors in Series and in pArallel

2. Resistors in Series
Series – describes a circuit or portion of a circuit that provides a single conducting path without junctions
When resistors are arranged in series, the current flowing through each resistor is the same
Equivalent resistance – the total resistance of a circuit

3. Resistors in Series

4. Resistors in Series
For resistors in series, the equivalent resistance is equal to the sum of all of the resistors
Req = R1 + R2 + R3…
Total Potential difference (voltage) = Current * Equivalent Resistance
VTot = IReq
The equivalent resistance of a series combination of resistors is always greater than any individual resistance

5. Resistors in Series
Potential difference across a given resistor can be calculated by multiplying the current (which is constant) by the resistance of the given resistor
V1 = IR1 or V2 = IR2
In a series circuit, all of the elements must be able to conduct electrical charge
If one bulb goes out or one wire gets disconnected, the entire circuit fails

6. Resistors in Series Resistors are placed in series to regulate current
Able to combine several small resistances to get a large overall resistance
May be a safety feature, such as in burglar alarms

7. Resistors in Parallel
Parallel – describes two or more components in a circuit that are connected across common points or junctions, providing separate conducting paths for the current
There is more than one pathway through the circuit or part of a circuit
Resistors in parallel have the same potential difference across them
V is constant
The sum of the individual currents in parallel resistors equals the total current
ITot = I1 + I2 + I3 …

8. Resistors in Parallel

9. Resistors in Parallel
The equivalent resistance of resistors in parallel can be calculated using a reciprocal relationship
1/Req = 1/R1 + 1/R2 + 1/R3 …
The equivalent resistance is always less than the smallest resistance in the group of resistors
Parallel circuits do not require all elements to conduct
The circuit will continue so long as there is at least one complete pathway from one terminal to the other

10. Resistors in Parallel