What does power input mean? Tick (✓) one box - AQA - GCSE Physics - Question 9 - 2019 - Paper 1

The equation that links these quantities is:

$P = V imes I$ where $P$ is power, $V$ is potential difference, and $I$ is current.

Given:

• Power input ($P$) = 40 W
• Potential difference ($V$) = 230 V

Using the formula:

$P = V imes I$

Rearranging gives:

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

Now substituting the values:

$I = \frac{40 ext{ W}}{230 ext{ V}} = 0.1739 ext{ A}$

The current in the light bulb is approximately 0.17 A.

The equation is:

$\text{Efficiency} = \frac{\text{Useful Power Output}}{\text{Total Power Input}}$

Assuming $X$ represents the useful power output, using the efficiency of 0.30:

$\text{Useful Power Output} = 0.30 \times 9.0 \text{ W} = 2.7 ext{ W}$

So, $X = 2.7$ W.

Light bulbs should also be labelled with the rate at which they emit visible light to inform consumers about their brightness. This helps consumers choose bulbs based on effectiveness for lighting purposes, as well as energy efficiency, thus allowing them to be more informed about potential energy waste.