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Figure 2 shows a circuit that a student built - AQA - GCSE Physics Combined Science - Question 4 - 2019 - Paper 1
Question 4
Figure 2 shows a circuit that a student built. The lamp has a resistance of 10 Ω Each resistor has a resistance of 10 Ω What is the total resistance of the circuit?... show full transcript
Worked Solution & Example Answer:Figure 2 shows a circuit that a student built - AQA - GCSE Physics Combined Science - Question 4 - 2019 - Paper 1
Step 1
The total resistance of the circuit?
Answer
The total resistance of the circuit is less than 20 Ω. This is because the resistors are in parallel, and the total resistance for resistors in parallel can be calculated using the formula:
Given that both the lamp and each resistor have a resistance of 10 Ω, when combined in parallel, the total resistance becomes less than the individual resistances.
Step 2
Explain your answer to Question 04.1
Answer
The resistance of the lamp is added to the total resistance of the resistors in parallel. In parallel circuits, the total resistance is always less than the smallest resistor value due to the multiple pathways for current. Thus, the combined resistance here will be less than 10 Ω, confirming that the total resistance is less than 20 Ω.
Step 3
Step 4
Explain how the current in the thermistor changed.
Answer
As the temperature of the thermistor increases, the resistance of the thermistor decreases. This decrease in resistance results in an increase in current, as per Ohm's Law, which states that current is inversely proportional to resistance for a given voltage.
Step 5
Explain how the potential difference across the resistor will change when the switch is closed.
Answer
When the switch is closed, the potential difference across the resistor becomes 0 V. This is because there is a short circuit across the resistor, allowing the current to bypass it entirely.
Step 6
Explain how the potential difference across the lamp will change when the switch is closed.
Answer
When the switch is closed, the potential difference across the lamp remains the same as the battery voltage. This is because the current now bypasses the resistor, ensuring that the lamp receives the full potential difference.