GCSE AQA Physics Combined Science Current, Potential Difference & Resistance: The camera in a mobile phone use

Question

The camera in a mobile phone uses an LED to provide light when taking a photograph.

A student investigated how the potential difference across an LED varies with the current in it.

Figure 9 shows the circuit used.

Figure 9

The student closed the switch. The voltmeter gave a reading of 5.0 V.
The ammeter gave a reading of 0 mA.
The LED did not emit any light.
Explain how the student should have changed the circuit to make the LED emit light.

The student changed the circuit so that the LED emitted light.
The current in the circuit was 290 mA.
The power of the LED was 0.98 W.
Calculate the potential difference across the LED.
Use the Physics Equations Sheet.
Give your answer to 2 significant figures.

Potential difference (2 significant figures) = ______ V

A traditional camera uses a flash unit to provide light.

Figure 10 shows a flash unit on a traditional camera.

Figure 10

The flash unit emits light from xenon gas in a fluorescent tube.
What happens when a xenon atom emits light?
Tick (✓) one box.

Electrons in the atom fall to a lower energy level. [ ]
Electrons in the atom move to a higher energy level. [ ]
Electrons leave the atom, causing ionisation. [ ]
Electrons transfer to the atom from the electrical circuit. [ ]

When the flash unit is used there is a mean potential difference of 200 V across the fluorescent tube.
The flash of light lasts for 2.8 × 10^−4 s.
1.4 J of energy is transferred.
Calculate the mean current.
Use the Physics Equations Sheet.

Mean current = ______ A

The camera in a mobile phone uses an LED to provide light when taking a photograph - AQA - GCSE Physics Combined Science - Question 5 - 2022 - Paper 1

Worked Solution & Example Answer:The camera in a mobile phone uses an LED to provide light when taking a photograph - AQA - GCSE Physics Combined Science - Question 5 - 2022 - Paper 1

05.1 Explain how the student should have changed the circuit to make the LED emit light.

05.2 Calculate the potential difference across the LED.

05.3 What happens when a xenon atom emits light?

05.4 Calculate the mean current.

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