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* (a) When the student moved the wire quickly downwards between the magnets, the reading on the balance changed - Edexcel - A-Level Physics - Question 15 - 2023 - Paper 4
Question 15
* (a) When the student moved the wire quickly downwards between the magnets, the reading on the balance changed. Explain how the reading on the balance changed. (b)... show full transcript
Worked Solution & Example Answer:* (a) When the student moved the wire quickly downwards between the magnets, the reading on the balance changed - Edexcel - A-Level Physics - Question 15 - 2023 - Paper 4
Step 1
When the student moved the wire quickly downwards between the magnets, the reading on the balance changed.
Answer
As the wire moves between the magnets, it cuts through the magnetic field lines created by the magnets. This motion induces an electromotive force (emf) in the wire due to electromagnetic induction. According to Lenz's Law, the induced current will create a magnetic field that opposes the change causing it. Because of this induced emf, the wire experiences a force which results in a change in tension.
Consequently, the reading on the balance will change as the force acting on the wire alters the overall load. As the wire moves down quickly, we can expect the reading to fluctuate, likely increasing while the descent occurs due to the wire's interaction with the magnetic field.
Step 2
Calculate the maximum p.d. that could have been measured.
Answer
To calculate the maximum potential difference (p.d.) that could have been measured, we can use the formula for induced emf:
where:
- is the magnetic flux density (0.35 T)
- is the effective length of the wire in the magnetic field (which is the height of each magnet, 20 mm or 0.02 m)
- is the vertical speed of the wire (2.2 m/s)
Substituting these values into the formula gives:
Hence, the maximum potential difference that could have been measured is approximately 0.0154 V.