| Aim | The objective of this experiment is to investigate how the potential difference (V) across a resistor varies with the current (I) passing through it and to determine the resistance of the resistor. Additionally, a graph of V versus I will be plotted. |
| Theory | Ohm’s law states that the potential difference (V) across a metallic wire is directly proportional to the current (I) flowing through it, as long as the temperature remains constant. This can be expressed mathematically as V∝I, or V=IR, where R is the resistance of the wire, and it remains constant for a given metallic wire. The resistance of a wire depends on several factors. These include the nature of the resistor, the length of the wire (as the length increases, the resistance also increases), and the cross-sectional area of the wire (as the cross-sectional area increases, the resistance decreases). |
| Equipment needed | Power supply Resistor (preferably one with a known resistance) Ammeter Voltmeter Connecting wires Graph paper Pen/pencil |
| Procedure | 1 .Set up the circuit by connecting the power supply to the resistor, ammeter, and voltmeter as shown in the diagram: Power supply (+) — Ammeter — Resistor — Voltmeter — Power supply (-) 2 .Turn on the power supply and adjust it to provide a low voltage (around 1-2V). 3 .Record the values of the current and voltage displayed on the ammeter and voltmeter, respectively. Repeat this step for different values of the current, increasing in steps of around 0.1-0.2 A. 4 .Use the recorded values to calculate the resistance of the resistor using Ohm’s Law, which states that V = IR, where V is the voltage across the resistor, I is the current passing through it, and R is the resistance of the resistor. Rearranging this equation gives R = V/I. 5 .Plot a graph of voltage (V) versus current (I) using the recorded values. To do this, use the voltage values for the y-axis and the current values for the x-axis. Use a suitable scale for both axes and plot the points corresponding to each value of V and I. 6 .Draw a best-fit line or curve through the points on the graph. The slope of this line/curve is equal to the resistance of the resistor. Calculate the resistance of the resistor from the slope of the graph. 7 .Repeat steps 3 to 7 for different values of the voltage, keeping the resistance of the resistor constant. 8 .Compare the values of the resistance obtained from the different voltage values and ensure that they are consistent. 9 .Finally, calculate the average value of the resistance from the different voltage values. |
| Circuit Diagram |  |
| Graph |  |