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Figure 7 shows a system to monitor a tank filling with liquid in which a magnet is mounted on a float - AQA - A-Level Physics - Question 3 - 2019 - Paper 8
Question 3
Figure 7 shows a system to monitor a tank filling with liquid in which a magnet is mounted on a float. The Hall effect sensor produces an output voltage $V$. $V$ de... show full transcript
Worked Solution & Example Answer:Figure 7 shows a system to monitor a tank filling with liquid in which a magnet is mounted on a float - AQA - A-Level Physics - Question 3 - 2019 - Paper 8
Step 1
Compare the advantages of the two arrangements for monitoring the movement of the magnet towards the Hall effect sensor.
Answer
With the north pole facing the sensor:
- Higher sensitivity and larger gradient over very short range.
- There is some ambiguity in liquid level due to peak in graph, meaning it may not correctly reference a single output reading.
With the south pole facing the sensor:
- Less sensitivity and smaller gradient but covers a larger range.
- There is no ambiguity in liquid level, since each level produces a discrete output up to saturation.
Step 2
Calculate the number of complete revolutions of the drive shaft in one second.
Answer
From Figure 10, there are approximately 2.4 divisions (5 ms/div) per complete cycle. Thus, for the period :
- Period time = 2.4 divisions × 5 ms/div = 12 ms.
The frequency can be found using the formula:
To find the number of revolutions in one second:
- Number of revolutions = frequency × time = rev.
Rounding down gives 83 full revolutions in one second.