# Series & Parallel Circuit Comparison

Series Parallel
Voltage Drop

## Series Circuits

• Closed Loop circuit with only one path where current may flow
• Used for Controls and Signaling mostly

Series Circuit Rules
Rule 1 Current total equals the current in any part of the circuit
Rule 2 Voltage total equals the sum of all voltages
Rule 3 Resistance total equals the sum of all resistances

Series circuit Total current: I=Es/Rt

Series Circuit Calculations:

1. Determine each circuit resistors resistance
2. Calculate circuit total resistance
• Rt = R1 + R2 + R3
3. Calculate the current
1. I = Es / Rt

### Series Circuit Summary

• Resistors are measured across
• Current is same value through all resistances
• Source voltage = Sum of all resistances voltage drops
• All resistances power consumed sum = Total power consumed by the circuit ## Parallel Circuits

• Open-Loop Circuit with more than one path for current to flow
• Voltage Drop across each resistance is equal to the voltage drop supplied by the power source
Parallel Circuit Rules
Rule 1 Current total equals the sum of all currents in all circuit branches
Rule 2  Voltage total equals the sum of all voltages
Rule 3  Resistance total is found by applying Ohm’s Law to the total values (Rt=Et/It) NEED SUPERSCRIPT CODE Note: Total resistance is always less than the resistance of any branch.

### 3 Methods to calculate Total Resistance in Parallel Circuits

• Equal Resistance
• Rt = 1 resistor Ω / number of resistors
• Note: All resistors must have same resistance
• Product-over-Sum
• Rt = (R1 x R2) / (R1 + R2)
• Note: Only uses 2 resistors per equation
• If more then 2 resistors, then use the equivalent resistance of the last 2 resistors as a ‘new’ resistance for the next equation
• Reciprocal
• Rt = 1/[(1/R1) + (1/R2) + (1/R3)…]
• Note: Preferred method because this can be used for as many resistors as contained within a circuit

### Parallel Circuit Summary

• Voltage is same across each circuit component
• Total power Consumed = Sum of the Power in all branches
• Ris always less then smallest individual resistor
• Rt calculation = 1/[(1/R1) + (1/R2) + (1/R3)…]
• Has 2 or more paths for current to flow
• Total Current = is provided by Source voltage and sum of all currents in all branches ### Series-Parallel Circuit Summary

Obtain different voltages of series circuits combined with different currents of parallel circuits

# Power Supplies

Series-ConnectedParallel-Connected
current constantcurrent increases

### Series-connected

• current constant

### Parallel-connected

• Voltage constant
• current increases

### Series-connected Delta/Delta

• Transformer power supply, 3Ø = 3 transformers connected in series 