HS2 Physics Chapter 3 Current Electricity: Experiments

 

Experiment 1: Verification of Ohm’s Law

Objective:
To verify Ohm's law by plotting a graph of potential difference (V) versus current (I).

Apparatus:

• Voltmeter

• Ammeter

• Resistor or resistance wire

• Battery or power supply

• Rheostat

• Connecting wires

• Switch

Procedure:

1. Set up the circuit with the resistor, voltmeter in parallel, and ammeter in series.

2. Adjust the rheostat to vary the current through the circuit.

3. For each setting, record the voltmeter and ammeter readings.

4. Repeat for at least 5 values.

5. Plot V vs I on a graph.

Expected Result:
The graph should be a straight line passing through the origin, confirming Ohm’s law.

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Experiment 2: Determination of Internal Resistance of a Cell

Objective:
To determine the internal resistance of a given cell using a potentiometer.

Apparatus:

• Potentiometer

• Cell

• Standard cell

• Galvanometer

• Resistance box

• Key

• Jockey

• Connecting wires

Procedure:

1. Connect the circuit as per the standard potentiometer setup.

2. Measure the potential difference across the cell when no current is drawn (open circuit).

3. Then measure the potential difference when the cell supplies current through a known external resistor.

4. Use the ratio of the potential differences and known resistance to calculate internal resistance using the formula:

$$r = R\left(\frac{V - V'}{V'}\right)$$

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Experiment 3: Measurement of Resistance Using Meter Bridge

Objective:
To determine the unknown resistance using a meter bridge (Wheatstone bridge principle).

Apparatus:

• Meter bridge

• Known resistance box

• Unknown resistor

• Galvanometer

• Jockey

• Battery

• Keys

• Connecting wires

Procedure:

1. Connect the known and unknown resistors on opposite sides of the meter bridge.

2. Connect the galvanometer and jockey as shown in the Wheatstone bridge setup.

3. Slide the jockey to find the null point (zero deflection).

4. Measure the lengths on either side and use:

$$\frac{R_1}{R_2} = \frac{l_1}{l_2}$$

to find the unknown resistance.