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10 (a) Figure 23 shows a model dynamo - Edexcel - GCSE Physics - Question 10 - 2023 - Paper 2
Question 10
10 (a) Figure 23 shows a model dynamo. The dynamo contains a coil of wire that can spin inside a permanent magnet. The dynamo produces a D.C output. A teacher con... show full transcript
Worked Solution & Example Answer:10 (a) Figure 23 shows a model dynamo - Edexcel - GCSE Physics - Question 10 - 2023 - Paper 2
Step 1
(i) Which row of the table shows how the rotation of the handle has changed between (a) and (b)?
Answer
The correct answer is C: slower than (b) and opposite to (b). This conclusion is based on the direction of the voltmeter readings in figures 24(a) and 24(b). Since the reading in (b) is opposite in direction and lower in value, it indicates a slower rotation.
Step 2
(ii) The teacher connects the dynamo to a lamp. Explain why it is more difficult to turn the dynamo when it is connected to a lamp.
Answer
When the dynamo is connected to a lamp, it generates electric current. This current creates a magnetic field that interacts with the coil's motion, generating a back-emf (electromotive force) that opposes the rotation. Therefore, the motor effect of the magnetic field generates a force that resists the rotation, making it more difficult to turn the dynamo.
Step 3
Calculate the potential difference across the secondary coil. Use an equation selected from the list of equations at the end of the paper.
Answer
To calculate the potential difference across the secondary coil, we use the transformer equation:
Substituting the known values gives:
Rearranging for yields:
Calculating this yields: