Figure 19 shows a lamp connected to a d.c - Edexcel - GCSE Physics - Question 8 - 2022 - Paper 1

The power supplied to the lamp can be calculated using the formula:

$\text{Power} = V \times I$

Substituting the known values:

• Voltage (V) = 4.5 V
• Current (I) = 0.30 A

Calculating:

$\text{Power} = 4.5 \times 0.30 = 1.35 W$

Thus, the power supplied to the lamp is approximately 1.4 W.

When another identical lamp is added in parallel, the total resistance in the circuit decreases because the resistance of multiple paths leads to an overall reduction in resistance.

This means:

• The total current from the power supply increases.
• Each lamp receives the same voltage (4.5 V) as in Figure 19.
• However, the total power drawn from the supply increases, causing the lamps in Figure 20 to have less brightness compared to the single lamp in Figure 19, as the current splits across the two lamps.

Key Points:

• The brightness of a lamp is directly related to the power it receives.
• In Figure 20, the increase in resistance due to adding another lamp decreases the power to each lamp, making them dimmer than the single lamp in Figure 19.

To measure the resistance of 50 cm of resistance wire, the circuit diagram should include:

• A low voltage power supply (battery)
• An ammeter in series to measure current
• A voltmeter in parallel to measure potential difference across the resistance wire
• Resistance wire identified clearly
• Taps for measuring only 50 cm of the wire

The diagram should clearly label each component according to standard circuit symbols.

Direct current (d.c.) flows in one direction only, ensuring a consistent flow of electrons. This is typical in batteries and other similar sources.

In contrast, alternating current (a.c.) changes direction periodically, reversing its current flow, which is commonly used in households and for powering appliances. This allows for efficient long-distance transmission of electricity.