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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 conne... 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: (a) slower than (b) and (a) opposite to (b). This indicates that it takes longer to rotate the handle in the second case, and the direction of rotation has reversed.
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, the electrical load increases the current flowing through the coil. This generates a stronger magnetic field, which creates an opposing force known as 'back EMF' (electromotive force), making it more difficult to rotate the handle. The increased magnetic interaction reduces the efficiency of energy transfer from mechanical work to electrical energy.
Step 3
Calculate the potential difference across the secondary coil.
Answer
To find the potential difference across the secondary coil, we use the transformer equation:
Substituting the known values into the equation:
Rearranging gives:
Calculate:
Thus, the potential difference across the secondary coil is approximately 5.2 V.