5 (a) Figure 10 shows two different types of the same circuit component - Edexcel - GCSE Physics Combined Science - Question 5 - 2021 - Paper 1

The correct way to connect an ammeter and a voltmeter in a circuit is given in Row C:

• Ammeter: in series
• Voltmeter: in parallel. This configuration ensures that the ammeter measures the current flowing through the component and the voltmeter measures the potential difference across it.

The graph in Figure 11 illustrates a nonlinear relationship between current and voltage. As voltage increases, the current also increases, but not in a linear manner. Initially, at lower voltage values, current rises gradually, indicating ohmic behavior, but as the voltage reaches higher levels, the current increases at an accelerated rate. This suggests that the filament lamp exhibits properties of a non-ohmic component, where resistance changes with temperature.

To calculate the resistance, we use the formula: $R = \frac{V}{I}$ Substituting the known values: $R = \frac{4.5}{51 \times 10^{-3}}$ Performing the calculation: $R = 88.24 \, \Omega$ Therefore, the resistance of the filament lamp is approximately 88.2 Ω.

As voltage increases across the filament lamp, the temperature of the filament rises due to the increased electrical power being supplied. Since the filament is made of a metal, it exhibits a positive temperature coefficient of resistance, meaning that as its temperature increases, its resistance also increases. Consequently, at higher voltages, the increase in filament temperature results in higher resistance, leading to a nonlinear current-voltage relationship.