# Resistance in Series & Parallel without Power Supply

2 September 2023

# Resistance in Series & Parallel without Power Supply

Resistance is a fundamental concept in electrical circuits. It determines how much a material or component opposes the flow of electric current. In most cases, resistance is measured using a power supply to provide the necessary voltage. However, there are situations where resistance can be analyzed without the need for a power supply.

## Resistance in Series

In a series circuit, resistors are connected end-to-end, creating a single path for current flow. The total resistance in a series circuit is the sum of the individual resistances. By measuring the voltage drop across each resistor and the total current flowing through the circuit, the resistance of each resistor can be calculated using Ohm’s Law (R = V/I).

### Example:

Consider a series circuit with three resistors: R1, R2, and R3. The voltage drop across R1 is 5V, R2 is 3V, and R3 is 2V. The total current flowing through the circuit is 2A. Using Ohm’s Law, we can calculate the resistance of each resistor:

- R1 = 5V / 2A = 2.5Ω
- R2 = 3V / 2A = 1.5Ω
- R3 = 2V / 2A = 1Ω

## Resistance in Parallel

In a parallel circuit, resistors are connected side by side, providing multiple paths for current flow. The total resistance in a parallel circuit can be calculated using the formula 1/Rt = 1/R1 + 1/R2 + 1/R3, where Rt is the total resistance and R1, R2, and R3 are the individual resistances.

### Example:

Consider a parallel circuit with three resistors: R1, R2, and R3. The resistance of R1 is 2Ω, R2 is 3Ω, and R3 is 4Ω. Using the formula for total resistance, we can calculate:

1/Rt = 1/2Ω + 1/3Ω + 1/4Ω = 13/12Ω

Rt = 12/13Ω ≈ 0.923Ω

## Frequently Asked Questions

#### Q: Can resistance be measured without a power supply?

A: Yes, resistance can be analyzed in circuits without the need for a power supply. By measuring voltage drops and current flow, the resistance of individual components can be calculated.

#### Q: What is the difference between resistance in series and parallel?

A: In a series circuit, resistors are connected end-to-end, while in a parallel circuit, resistors are connected side by side. The total resistance in a series circuit is the sum of the individual resistances, while in a parallel circuit, it is calculated using the formula 1/Rt = 1/R1 + 1/R2 + 1/R3.

## Conclusion

Understanding resistance in series and parallel circuits is essential for analyzing and designing electrical circuits. By measuring voltage drops and current flow, the resistance of individual components can be determined without the need for a power supply. This knowledge is valuable in various applications, from electronics to electrical engineering.