A student wants to investigate how the current through a filament lamp affects its resistance - AQA - GCSE Physics - Question 5 - 2018 - Paper 1

To investigate the effect of current on the resistance of the filament lamp, the student can:

1. Set up the circuit with the components as described above.
2. Adjust the variable resistor to change the current flowing through the filament lamp.
3. Record the readings from the ammeter to measure current and the voltmeter to measure potential difference at various current settings.
4. Calculate the resistance of the lamp using Ohm's Law, $R = \frac{V}{I}$, where $V$ is the potential difference and $I$ is the current.

As the current through the filament lamp increases, the resistance of the filament lamp also changes due to the heating effect. Initially, the resistance may decrease as the filament heats up, but at higher currents, the resistance tends to increase as the filament temperature rises significantly, leading to increased atomic lattice vibrations that impede the flow of electrons.

To estimate the resistance of the filament lamp at a current of 0.10 A, refer to the relevant point on Figure 6. If the voltmeter reading at this current is, for example, 3 V, then the resistance can be calculated as: $R = \frac{V}{I} = \frac{3 \, \text{V}}{0.10 \, \text{A}} = 30 \, \Omega$

Based on the characteristics of the graphs:

• Graph A: Filament lamp (non-linear relationship)
• Graph B: Resistor at constant temperature (linear relationship)
• Graph C: Diode (non-linear with a threshold).