Keywords: IGCSE Prescribed Practical, Resistivity, Wire, Physics, Resistance, Length, Diameter, Ohm’s Law, Calculations, Experiment

Introduction: In this IGCSE Prescribed Practical experiment, we will investigate the resistivity of a wire. Resistivity is a measure of how much a material opposes the flow of electric current, and it is an intrinsic property of the material. To calculate the resistivity of a wire, we need to measure its resistance, length, and diameter. By understanding resistivity, we can better choose materials for various applications in the field of physics and engineering.

Equipment Needed:

1. Wire of known length and diameter (e.g., a copper wire)
2. Micrometer screw gauge
3. Meter ruler
4. Ohmmeter or multimeter (set to measure resistance)
5. Crocodile clips
6. Connecting wires

Step by Step Method:

1. Measure the length of the wire using the meter ruler and record the value (L).
2. Use the micrometer screw gauge to measure the diameter (d) of the wire. Repeat this measurement at three different points along the wire and take the average to get a more accurate value.
3. Set up the ohmmeter or multimeter to measure resistance.
4. Connect one end of the wire to the ohmmeter using a crocodile clip and a connecting wire.
5. Attach the other crocodile clip to the other end of the wire and connect it to the ohmmeter using another connecting wire.
6. Turn on the ohmmeter and record the resistance (R) displayed.
7. Calculate the cross-sectional area (A) of the wire using the formula: A = π(d/2)^2
8. Calculate the resistivity (ρ) using the formula: ρ = R*A / L

Expected Findings and Calculations: The resistivity of a wire depends on the material it is made of. In this experiment, we will calculate the resistivity (ρ) using the measured resistance (R), the length (L), and the cross-sectional area (A) of the wire.

Resistivity formula: ρ = RA / L

Conclusion: By following the steps outlined in this IGCSE Prescribed Practical experiment, you will be able to measure the resistivity of a wire. Understanding resistivity is crucial for selecting appropriate materials for various applications in physics and engineering.

Questions:

1. What is resistivity?
2. How can you calculate the cross-sectional area of a wire?
3. What is the formula to calculate resistivity?
4. Why is it important to measure the diameter of the wire at three different points?
5. Can you name a material with high resistivity and one with low resistivity?

Answers:

1. Resistivity is a measure of how much a material opposes the flow of electric current. It is an intrinsic property of the material.
2. The cross-sectional area of a wire can be calculated using the formula: A = π(d/2)^2, where d is the diameter of the wire.
3. The formula to calculate resistivity is: ρ = RA / L, where R is the resistance, A is the cross-sectional area, and L is the length of the wire.
4. Measuring the diameter at three different points helps to account for any irregularities in the wire’s diameter, providing a more accurate average value.
5. A material with high resistivity is glass, while a material with low resistivity is copper.

• Practical Physics