Q25 · 2024 · Paper 1Simple familiar4 marks
QUESTION 25 (4 marks)
A transformer with a turns ratio of 48:1 is set up to reduce a 240 V input.
a)[3 marks]
Explain how a transformer works in terms of Faraday’s Law and electromagnetic induction.
b)[1 mark]
Determine the output voltage. Voltage = V
WORKED SOLUTION
4 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
According to Faraday’s Law, when the magnetic flux linking a
circuit changes, an emf is induced in the circuit proportional to the
rate of change of the flux linkage.
Therefore, in the transformer, the changing voltage in the primary
coil will affect the rate of change of the magnetic flux in the
second coil. Although the circuits aren’t connected, a current will
be induced in the secondary circuit.
A current will be induced in the second coil generating an AC
voltage of:
4
5 V
240
8
1
p
p
s
s
s
s
V
n
V
V
n
V
=
=
=
• describes Faraday’s Law [1 mark]
• explains changing voltage in the primary
coil affects rate of change of magnetic flux
in secondary coil [1 mark]
• explains an AC voltage is induced in the
secondary coil by electromagnetic induction
[1 mark]
• determines secondary voltage to be 5 V
[1 mark]
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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