Figure 3 shows an LED torch. The torch contains one LED, one switch and three cells. Which diagram shows the correct circuit for the torch? Tick (✔) one box. Write down the equation which links charge flow (Q), current (I) and time (t). The torch worked for 14 400 seconds before the cells needed replacing. The current in the LED was 50 mA. Calculate the total charge flow through the cells. Write down the equation which links efficiency, total power input and useful power output. The total power input to the LED was 0.24 W. The efficiency of the LED was 0.75. Calculate the useful power output of the LED.

GCSE AQA Physics Current, Potential Difference & Resistance: Figure 3 shows an LED torch. Th

Figure 3 shows an LED torch - AQA - GCSE Physics - Question 2 - 2020 - Paper 1

Question 2

Figure 3 shows an LED torch. The torch contains one LED, one switch and three cells. Which diagram shows the correct circuit for the torch? Tick (✔) one box. Writ... show full transcript

Worked Solution & Example Answer:Figure 3 shows an LED torch - AQA - GCSE Physics - Question 2 - 2020 - Paper 1

Step 1

Write down the equation which links charge flow (Q), current (I) and time (t).

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Answer

The equation that links charge flow (Q), current (I), and time (t) is given by:

$Q = I imes t$

Step 2

Calculate the total charge flow.

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Answer

To calculate the total charge flow through the cells, we substitute the given values into the equation:

$I = 50 ext{ mA} = 0.050 ext{ A}$ $t = 14 400 ext{ seconds}$

Now substituting these values into the equation:
$Q = 0.050 ext{ A} imes 14 400 ext{ s}$ $Q = 720 ext{ C}$

Step 3

Write down the equation which links efficiency, total power input and useful power output.

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Answer

The equation that links efficiency, total power input, and useful power output is:

$Efficiency = \frac{Useful \ power \ output}{Total \ power \ input}$

Step 4

Calculate the useful power output of the LED.

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Answer

Given:

Total power input = 0.24 W
Efficiency = 0.75

We can rearrange the equation to find the useful power output:

$Useful \ power \ output = Efficiency \times Total \ power \ input$ Substituting the values: $Useful \ power \ output = 0.75 \times 0.24 = 0.18 \text{ W}$

Figure 3 shows an LED torch - AQA - GCSE Physics - Question 2 - 2020 - Paper 1

Worked Solution & Example Answer:Figure 3 shows an LED torch - AQA - GCSE Physics - Question 2 - 2020 - Paper 1

Write down the equation which links charge flow (Q), current (I) and time (t).

Calculate the total charge flow.

Write down the equation which links efficiency, total power input and useful power output.

Calculate the useful power output of the LED.

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