AQA GCSE Physics (8463), Higher tier · Magnetism and electromagnetism › Induced potential and transformers
Practise Uses of the generator effect. 12 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Which type of current does each of these generators produce? alternator dynamo
Alternator: ac. Dynamo: dc.
Name the component in an alternator that connects the rotating coil to the external circuit without twisting the wires.
Slip rings
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
The generator effect is used in alternators and in dynamos.
(a) Which type of current does each of these generators produce? alternator dynamo[2]
(b) Which part of a dynamo makes the current in the external circuit always flow in the same direction? Tick (✓) one box.[1]
The brushes
The iron core
The slip rings
The split-ring commutator
(c) Give one use of an alternator.[1]
Show the answer and mark scheme
(a)Answer: Alternator: ac. Dynamo: dc.
alternator: alternating current (ac)
dynamo: direct current (dc)
(b)Answer: The split-ring commutator
(c)Answer: Generating electricity in a power station.
generating electricity in a power station / in a car (to charge the battery) / in a wind turbine
Question 2Medium2 marks
A wind turbine uses the wind to turn a coil inside a magnetic field, generating electricity by the generator effect.
Explain why a wind turbine generates more electrical power on a windy day than on a day with only a gentle breeze.[2]
Show the answer and mark scheme
Answer: A stronger wind spins the coil faster, so it cuts field lines more quickly and induces a greater potential difference, generating more power.
a stronger wind turns the coil faster (at a higher rotational speed)
the coil then cuts magnetic field lines more quickly, inducing a greater potential difference (and current), so more electrical power is generated
Question 3Hard6 marks
A simple alternator has a rectangular coil that is rotated between the poles of a magnet. The ends of the coil are connected to slip rings.
Explain how the alternator produces an alternating potential difference, and describe how the output changes if the coil is rotated faster.[6]
Show the answer and mark scheme
Answer: Level-of-response answer: the rotating coil cuts field lines, inducing a pd that reverses every half turn (ac) via slip rings; faster rotation gives a larger peak pd and a higher frequency.
the coil is rotated in the magnetic field
the sides of the coil cut the magnetic field lines / the field through the coil keeps changing
so a potential difference is induced across the coil (generator effect)
each side of the coil moves up through the field for half a turn and down for the next half turn
so the induced potential difference reverses direction every half turn: it is alternating
the potential difference is largest when the sides move at right angles to the field and zero when they move parallel to it
the slip rings and brushes connect the rotating coil to the external circuit without the wires twisting
rotating faster increases the peak potential difference
rotating faster also increases the frequency (shorter period)
Marked with levels of response: the full level descriptors are in the app.