2. Study the dependence of potential difference (v) across a resistor on the current (I) passing through it and determine its resistance. Also plot a graph of V and I.

Aim:- To study the dependence of potential difference (v) across a resistor on the current (I) passing through it and determine its resistance. Also plot a graph of V and I.

Materials Required:- A dry cell with terminals, 10 pieces of thick insulated copper wire with bare ends, a single key, an ammeter, a voltmeter, a rheostat, a resistor of approximately 2Ω resistor, sand paper.

Symbolic Circuit Diagram

Observation and Calculations:-

S. No.	Current (in Ampere)	Potential Difference (in volts)	Resistance of Resistor A (in ohms)
1.	0.125	0.375	3 Ω
2.	0.25	0.75	3 Ω
3.	0.50	1.5	3 Ω
4.	0,75	2.25	3 Ω

Dependence of Potential Difference across a resistor.

Conclusions:-

For Table:

1. As the ratio of V and I is a constant quantity R, therefore V α I. This verifies Ohm’s law, which states that potential difference at the ends of a conductor is directly proportional to the current flowing through it, provided all physical properties of the conductor remains same.
2. The resistance of the conductor is the ratio of potential difference and the current.

For Graph:

1. As graph is straight line, therefore V α I. This verifies the Ohm’s law.
2. The slope of the graph V/I is the magnitude of resistance.

Precautions:-

1. Clean the ends of connecting wires by sand paper.
2. Make tight connections while connecting various elements of the circuit.
3. Remove the plug key when you have finished your readings.

Sources Of Errors:-

1. The value of the resistance is likely to change if the connections are not tight or the ends of copper wire are not clean.
2. The values of the resistance is likely to change, if the heavy current is passed through circuit or the circuit is switched on for a long time.