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AimThe 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.
TheoryOhm’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 neededPower supply
Resistor (preferably one with a known resistance)
Connecting wires
Graph paper
Procedure1 .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