Required Practical 4: Investigating Current and Potential Difference Across Components

In this practical, you will investigate the behaviour of different components, specifically a filament bulb, an ohmic resistor, and a diode. You will compare their resistance and how it changes as the current through them changes.

Equipment Needed:

• Power supply

• Ammeter

• Voltmeter

• Filament bulb

• Ohmic resistor

• Diode

• Connecting wires

Procedure:

1. Set up the circuit.

2. Start by connecting only the filament bulb to the circuit. Make sure the power supply is turned off.

3. Turn on the power supply and note down the ammeter reading (current) and voltmeter reading (voltage) across the filament bulb.

4. Turn off the power supply and disconnect the filament bulb.

5. Repeat steps 2-4 for the ohmic resistor and the diode separately.

Observations and Analysis:

1. Filament Bulb:

   • As you gradually increase the voltage (and therefore the current) across the filament bulb, you will observe that the brightness of the bulb increases steadily.

   • The resistance of the filament bulb increases as the current through it increases. This is evident from the fact that the ammeter reading increases while the voltmeter reading also increases, but not proportionally.

2. Ohmic Resistor:

   • The ohmic resistor will show a linear relationship between voltage and current. This means that as you increase the voltage, the current increases proportionally.

   • The resistance of an ohmic resistor remains constant, regardless of the current passing through it. This is why the ammeter and voltmeter readings will change in a linear fashion.

3. Diode:

   • The diode behaves differently from the other components. When connected in the correct orientation, it will allow current to flow only in one direction (forward bias), and you will observe a relatively low resistance.

   • When you reverse the direction of the diode (reverse bias), it will behave like an open circuit, allowing very little current to pass through it. The resistance in this direction is significantly high.

Conclusion:

• The filament bulb shows non-linear behaviour, with its resistance increasing as the current increases.

• The ohmic resistor demonstrates linear behaviour, maintaining a constant resistance as the current changes.

• The diode behaves as a one-way conductor, with low resistance in one direction (forward bias) and high resistance in the other direction (reverse bias).

This practical experiment highlights the differences in behaviour among different components and helps you understand how their resistance changes with varying current. It also provides insights into the fundamental concepts of resistance and the characteristics of different electrical components.

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