6(a) Figure 8 shows identical filament lamps connected together to a 12V power supply - Edexcel - GCSE Physics Combined Science - Question 6 - 2018 - Paper 1

Given that the power output (P) of each lamp is 0.75W, we can use the formula relating power, voltage, and resistance:

$P = \frac{V^2}{R}$

Where V is the potential difference across the lamp (1.5V) and R is the resistance. We rearrange this formula to find R:

$R = \frac{V^2}{P}$

Substituting the known values:

$R = \frac{(1.5)^2}{0.75} = \frac{2.25}{0.75} = 3.0 \Omega$

Thus, the resistance of each lamp is 3.0 Ω.

To investigate how the resistance of a single lamp changes with varying potential difference, the following steps can be taken:

1. Circuit Diagram: Draw a circuit diagram that includes a power supply, an ammeter, a voltmeter, the filament lamp, and a variable resistor (rheostat) to adjust the voltage.

2. Setup: Connect the circuit such that the power supply feeds into the variable resistor, then into the lamp, while the ammeter is placed in series with the lamp and the voltmeter in parallel across the lamp.

3. Varying Voltage: Adjust the variable resistor to change the potential difference across the lamp.

4. Measurement: For each voltage, measure the current flowing through the lamp using the ammeter and the potential difference across the lamp using the voltmeter.

5. Calculate Resistance: Use Ohm's Law, which states that:

$R = \frac{V}{I}$

to calculate the resistance at each voltage by substituting the measured current and voltage into the formula.

6. Record and Compare: Record the data in a table to analyze how the resistance changes as the potential difference varies.