Resistance of a Wire - GCSE Science Required Practical

Summary

This script outlines an experiment to study how resistance in a wire varies with its length using a high-resistance nichrome wire. The setup involves a series circuit with a battery, ammeter, and voltmeter. Measurements are taken from 100 cm to 30 cm, calculating resistance using Ohm's law. The goal is to plot resistance against length and observe the relationship, ensuring the circuit is disconnected between readings to prevent wire heating that could alter resistance.

Takeaways

• 🔬 The experiment investigates the relationship between the resistance of a wire and its length, using a nichrome wire due to its higher resistance compared to copper.
• 📏 A meter-long nichrome wire is used, measured against a ruler for precise length determination during the experiment.
• 🔌 The setup includes a series circuit with a battery, ammeter, and the resistance wire, ensuring both current and potential difference can be measured.
• 🔋 The voltmeter is connected in parallel to the resistance wire to measure potential difference across it.
• ⚡ The experiment starts with the wire at its full length of 100 centimeters and progressively measures at shorter lengths down to 30 centimeters.
• 💡 Shorter wire lengths can cause the wire to heat up due to increased current, which can alter resistance and affect the experiment's accuracy.
• 📊 Data collected includes voltage and current readings at various wire lengths, which are used to calculate resistance using Ohm's law (V = IR).
• ✅ It's crucial to disconnect the circuit between measurements to prevent the wire from overheating and to maintain accurate resistance readings.
• 📈 The results are plotted as a graph with resistance on the y-axis and length on the x-axis, expected to show a straight line with a positive gradient.
• 🔌 Proper circuit connection and disconnection are emphasized for safety and to ensure the wire's resistance is not altered by continuous current flow.

Q & A

What is the purpose of the experiment described in the script?

The purpose of the experiment is to investigate how the resistance of a wire changes with its length.

Why is nichrome wire used instead of copper wire in this experiment?

Nichrome wire is used because it has a higher resistance, which is easier to measure compared to the low resistance of copper wire.

What is the initial length of the nichrome wire used in the experiment?

The initial length of the nichrome wire used is one meter.

What is the role of the ammeter and voltmeter in the circuit?

The ammeter is used to measure the current flowing through the wire, while the voltmeter measures the potential difference across the wire.

Why is a double length cable used to connect the ammeter and voltmeter?

A double length cable is used to ensure there is enough reach to make the connections without struggling, especially when measuring longer lengths of wire.

What is the significance of keeping the wire taut on the meter ruler during the experiment?

Keeping the wire taut ensures accurate measurement of the wire's length and prevents any slack that could introduce errors into the results.

Why does the experiment stop at 30 centimeters?

The experiment stops at 30 centimeters because at shorter lengths, the resistance is too small, leading to a large current that causes the wire to heat up, which in turn changes its resistance and affects the experiment's results.

How is the resistance of the wire calculated for each length?

The resistance for each length is calculated by dividing the potential difference (voltage) by the current, following Ohm's law.

What is the importance of disconnecting the circuit between each reading?

Disconnecting the circuit between each reading prevents the wire from overheating due to continuous current flow, which could change its resistance and affect the accuracy of the experiment.

What is the expected outcome when plotting resistance against length on a graph?

The expected outcome is a straight line of best fit with a positive gradient, ideally passing through the origin (0,0), indicating a direct proportionality between resistance and length.