AQA GCSE Physics (8463), Higher tier · Magnetism and electromagnetism › The motor effect
Practise Electromagnetism. 14 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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When there is a current in a wire, what is produced around the wire?
A magnetic field
A solenoid is a long coil of wire. When there is a current in the solenoid, it produces a magnetic field. Describe the magnetic field inside the solenoid.
Strong and uniform.
A large direct current is switched on in the wire. Describe what happens to the compasses.
The needles turn so that together they form a circle around the wire.
What is a solenoid?
A long coil of wire.
Give one way to reverse the polarity (which end is the north pole) of an electromagnet, without changing anything about the coil itself.
Reverse the direction of the current.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
(a) When there is a current in a wire, what is produced around the wire?[1]
(b) Give two factors that affect the strength of the magnetic field at a point near a straight wire.[2]
(c) Describe the shape of the magnetic field lines around a long, straight wire that is carrying a current.[1]
(d) What is an electromagnet? Tick (✓) one box.[1]
A solenoid with an iron core
A solenoid with a copper core
A permanent magnet made of steel
A straight wire carrying a current
Show the answer and mark scheme
(a)Answer: A magnetic field
a magnetic field
(b)Answer: The size of the current and the distance from the wire.
the size of the current (in the wire)
the distance from the wire
(c)Answer: Concentric circles centred on the wire.
(concentric) circles around the wire
(d)Answer: A solenoid with an iron core
Question 2Medium8 marks
A solenoid is a long coil of wire. When there is a current in the solenoid, it produces a magnetic field.
(a) Describe the magnetic field inside the solenoid.[2]
(b) Describe the shape of the magnetic field outside the solenoid.[1]
(c) Give three ways of increasing the strength of the magnetic field of the solenoid.[3]
(d) Electromagnets are used on cranes in scrapyards to lift old cars. Explain why an electromagnet is more useful for this than a permanent magnet.[2]
Show the answer and mark scheme
(a)Answer: Strong and uniform.
strong
uniform / the field lines are parallel and equally spaced
(b)Answer: Like the field around a bar magnet.
similar to the field of a bar magnet
(c)Answer: Increase the current, add an iron core, use more turns of wire.
increase the current
put an iron core inside the solenoid
increase the number of turns (on the same length of solenoid)
(d)Answer: It can be switched off, so the crane can release the car.
an electromagnet can be switched on and off
so the car can be picked up and then released (dropped) where it is needed
Question 3Hard7 marks
A scrapyard needs a magnet to lift and sort scrap steel cars.
(a) Evaluate whether an electromagnet or a permanent magnet of similar size would be more suitable for this job.[3]
(b) The scrapyard's electromagnet can exert a maximum upward force of 25 000 N on a car. Calculate the greatest upward acceleration it could give a car of mass 1200 kg. Gravitational field strength = 9.8 N/kg.[4]
Show the answer and mark scheme
(a)Answer: An electromagnet is far more suitable, mainly because it can be switched off to release the load in a controlled way, which a permanent magnet cannot easily do.
an electromagnet can be switched on to grip the car and switched off to release it exactly where needed, whereas a permanent magnet's pull cannot easily be switched off, making it hard to release a heavy load in a controlled way
an electromagnet's strength can be adjusted (e.g. by changing the current), which is not possible with a permanent magnet
overall, an electromagnet is much more suitable for this job, because the ability to switch the field on and off is essential