Some students investigate electric circuits - Edexcel - GCSE Physics - Question 3 - 2012 - Paper 1

In this step, place the ammeter in series with the lamp to measure the current flowing through it, and place the voltmeter in parallel across the lamp to measure the potential difference.

To calculate the voltage across the lamp, we use Ohm's Law given by the formula:

$V = I imes R$

Where:

• $I = 0.5$ A (current)
• $R = 8$ Ω (resistance)

Thus, $V = 0.5 imes 8 = 4$ V.

The potential difference across the lamp is 4 V.

In the lamp, not all electrical energy is converted to light energy due to inefficiencies such as heat loss. The filament of the lamp heats up when current flows through it, and a significant portion of the energy is dissipated as heat rather than being transformed into visible light.

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

$P = V imes I$

Where:

• $V = 5$ V (potential difference)
• $I = 0.4$ A (current)

Thus, $P = 5 imes 0.4 = 2$ W.

The power being supplied to the lamp is 2 W.