IGCSE Physics 0625

4.2.1 Electric Charge

Objective: Describe an experiment to distinguish between electrical conductors and insulators.

Conductors are materials that allow electric current to flow through them easily. This is because they have a large number of free electrons that can move and carry charge. Insulators are materials that resist the flow of electric current. They have very few free electrons.

Experiment: Investigating Conductivity

The following describes an experiment to distinguish between conductors and insulators. The experiment involves using a simple circuit with a battery, a switch, a variable resistor, and different materials.

Apparatus

• Battery (e.g., 1.5V or 9V)
• Switch
• Variable resistor (e.g., 100Ω - 1kΩ)
• Connecting wires
• Various materials to test (e.g., copper wire, plastic ruler, glass rod, wood, metal spoon, rubber band)
• Multimeter (optional, for measuring voltage and current)

Circuit Diagram

Procedure

1. Construct a simple circuit using the battery, switch, and variable resistor. Ensure the circuit is complete.
2. Connect one end of the variable resistor to one terminal of the battery and the other end to one terminal of the switch.
3. Connect the other terminal of the switch to the component (the material being tested) using connecting wires.
4. If using a multimeter, connect it in series with the circuit to measure the voltage and current.
5. Close the switch and observe if the current flows through the circuit.
6. Record whether the current flows or not for each material tested.

Observations and Results

Conductors: When a conductor (e.g., copper wire, metal spoon) is used, the current will flow through the circuit, and the variable resistor will light up (if connected to a bulb). The multimeter will show a measurable voltage and current.

Insulators: When an insulator (e.g., plastic ruler, glass rod, wood, rubber band) is used, the current will not flow through the circuit. The variable resistor will not light up (if connected to a bulb), and the multimeter will show no or negligible voltage and current.

Conclusion

By observing whether a current flows through the circuit with different materials, we can distinguish between conductors and insulators. Conductors allow electric current to flow easily, while insulators resist the flow of electric current.

Safety Precautions: Always use a low voltage battery to avoid electric shock. Ensure the circuit is properly constructed to prevent short circuits.