Experiment 8: Resistance and Ohm’s Law

8.1 Introduction

Ohm’s Law is a fundamental principle in electrical circuits that relates the current flowing through a conductor to the voltage across it and the resistance it encounters. It is expressed mathematically as:

$$V=I\times R$$

Where:

• $V$ is the voltage (in volts),
• $I$ is the current (in amperes),
• $R$ is the resistance (in ohms).

This law serves as the foundation for understanding how electrical circuits operate. Resistance is the property of a material that opposes the flow of electric current, and it plays a critical role in determining how much current flows for a given voltage. This experiment will investigate the relationship between voltage, current, and resistance using a simple resistive circuit.

Purpose of the Experiment
The main objective of this experiment is to verify Ohm’s Law by measuring the current in a circuit with a known resistance and applied voltage. Additionally, this experiment aims to determine how the resistance of a resistor affects the current flow when the voltage is kept constant.

Theory
Ohm’s Law demonstrates that the current through a resistor is directly proportional to the voltage applied across it, provided the temperature and physical properties of the conductor remain constant. When voltage increases, the current increases proportionally, assuming resistance remains constant. Similarly, if the resistance of the circuit increases while keeping the voltage constant, the current will decrease.

Key Concepts:

• Resistance ($R$): The opposition to the flow of electric current, measured in ohms ($\Omega$).
• Voltage ($V$): The potential difference that drives current through a circuit, measured in volts (V).
• Current ($I$): The flow of electric charge through a conductor, measured in amperes (A).

The resistance of a conductor depends on several factors such as material, length, cross-sectional area, and temperature. For this experiment, we will assume that the resistance remains constant and is determined by the properties of the resistor used in the circuit.

Experimental Setup
In this experiment, a simple electrical circuit will be constructed consisting of a power source (battery), a resistor, and an ammeter to measure the current. The voltage across the resistor will be varied, and the corresponding current will be recorded. By plotting the voltage versus current, the slope of the line will give the value of the resistance according to Ohm’s Law.

This experiment is vital in understanding the fundamental behavior of electrical circuits and the practical applications of Ohm’s Law in everyday electronics.