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 Series & Parallel Circuits: 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, current, and time is given by:

$Q = I imes t$

where:

$Q$ is the charge flow in coulombs (C)
$I$ is the current in amperes (A)
$t$ is the time in seconds (s)

Step 2

Calculate the total charge flow through the cells.

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Answer

To calculate the total charge flow through the cells, use the equation from the previous step:

Convert the current from milliamperes to amperes:

$I = 50 ext{ mA} = 0.050 ext{ A}$
Substitute the values into the equation:

$Q = 0.050 imes 14,400$
Calculate:

$Q = 720 ext{ C}$

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 ( $ext{Efficiency}$ ), total power input ( $P_{ ext{input}}$ ), and useful power output ( $P_{ ext{output}}$ ) is:

$ext{Efficiency} = \frac{P_{ ext{output}}}{P_{ ext{input}}}$

Step 4

Calculate the useful power output of the LED.

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Answer

To find the useful power output, rearrange the efficiency equation:

Substitute the known values:

$0.75 = \frac{P_{ ext{output}}}{0.24}$
Solve for $P_{ ext{output}}$ :

$P_{ ext{output}} = 0.75 imes 0.24$
Calculate:

$P_{ ext{output}} = 0.18 ext{ W}$

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 through the cells.

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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