6(a) A technician investigates a light-dependent resistor (LDR) connected in series with a 120 Ω resistor and a voltage source. The technician measures the voltage across the LDR and also the current in the LDR. (i) Which one of these circuits should the technician use? Put a cross (X) in the box next to your answer. A B C D (ii) When the LDR is in bright sunlight, its resistance is 185 Ω. The voltage across the LDR is then 7.2 V. Show that the current in the LDR is about 0.039 A. (2) (iii) (4) (iv) An explanation to include The resistance (of the LDR) changes Greater resistance when in the dark

GCSE Edexcel Physics Core practical: Electrical circuits: 6(a) A technician investigates a

6(a) A technician investigates a light-dependent resistor (LDR) connected in series with a 120 Ω resistor and a voltage source - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1

Question 6

6(a)-A-technician-investigates-a-light-dependent-resistor-(LDR)-connected-in-series-with-a-120-Ω-resistor-and-a-voltage-source-Edexcel-GCSE Physics-Question 6-2015-Paper 1.png

6(a) A technician investigates a light-dependent resistor (LDR) connected in series with a 120 Ω resistor and a voltage source. The technician measures the voltage ... show full transcript

Worked Solution & Example Answer:6(a) A technician investigates a light-dependent resistor (LDR) connected in series with a 120 Ω resistor and a voltage source - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1

Step 1

Which one of these circuits should the technician use?

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Answer

The technician should use circuit B. This configuration allows for accurate measurement of the voltage across the LDR while ensuring that the circuit operates correctly with the given components.

Step 2

Show that the current in the LDR is about 0.039 A.

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Answer

To find the current through the LDR, we use Ohm's law, which states:

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

Substituting the given values:

Resistance of LDR: $R = 185 \Omega$
Voltage across LDR: $V = 7.2 V$

Thus, the current calculation is:

$I = \frac{7.2}{185} \approx 0.0389 A$

This is approximately 0.039 A.

Step 3

Which circuit has the same as?

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Answer

The answer is circuit C, as it provides a suitable arrangement for measuring the current in the circuit.

Step 4

Explain how the resistance of the LDR changes.

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Answer

The resistance of the LDR decreases when exposed to light, meaning it has less resistance in bright conditions. Conversely, the resistance is greater in darker conditions, which restricts current flow.

6(a) A technician investigates a light-dependent resistor (LDR) connected in series with a 120 Ω resistor and a voltage source - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1

Worked Solution & Example Answer:6(a) A technician investigates a light-dependent resistor (LDR) connected in series with a 120 Ω resistor and a voltage source - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1

Which one of these circuits should the technician use?

Show that the current in the LDR is about 0.039 A.

Which circuit has the same as?

Explain how the resistance of the LDR changes.

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