Evaluate — 3 marks
A scrapyard uses an electromagnet suspended from a crane to lift ferrous metal waste. The electromagnet consists of an iron core wrapped with copper wire connected to a power supply. A worker suggests that once the power is switched off, the electromagnet will lose all its magnetism instantly. However, the supervisor notices that some metal scraps occasionally stick to the electromagnet briefly after the power is turned off.
-
Explain why some metal scraps remain briefly attached to the electromagnet after the power supply is switched off.
[1 mark]
-
The iron core retains some magnetism after the power is switched off, while a steel core would retain significantly more. Evaluate which material would be more suitable for this scrapyard application and justify your answer with reference to permanent and induced magnetism.
[2 marks]
Show mark scheme
Compare — 4 marks
A scrapyard uses two different magnetic devices to separate metal waste. Device A is a permanent magnet made from iron, while Device B is an electromagnet that can be switched on and off. Both devices are used to pick up steel objects from a pile of mixed waste.
-
Compare the magnetic properties of the permanent magnet (Device A) and the electromagnet (Device B). [2 marks]
[2 marks]
-
Explain why the electromagnet (Device B) is more suitable for use in a scrapyard than the permanent magnet (Device A). [1 mark]
[1 mark]
-
When Device B is switched off, some steel objects remain attached to it. Explain what has happened to the steel and why this occurs. [1 mark]
[1 mark]
Show mark scheme
Evaluate — 5 marks
A scrapyard manager needs to choose between two methods for separating iron from a pile of mixed metals. Method A uses a permanent magnet attached to a crane. Method B uses an electromagnet powered by a battery. The manager wants the system that is most efficient and practical for daily use.
-
Explain the difference between how a permanent magnet and an electromagnet produce their magnetic fields.
[2 marks]
-
Evaluate which method (A or B) would be more suitable for the scrapyard. Consider the advantages and disadvantages of each approach.
[2 marks]
-
The electromagnet in Method B can be switched off to release the metal. Explain why a permanent magnet cannot achieve this, and suggest one modification that could make a permanent magnet system more practical for this application.
[1 mark]
Show mark scheme
Compare — 3 marks
A student is investigating two magnets in a school laboratory. One magnet is a permanent bar magnet made from iron. The other is an electromagnet made by wrapping wire around an iron core and connecting it to a power supply.
-
Compare the magnetic properties of the permanent bar magnet and the electromagnet when the power supply is switched on.
[2 marks]
-
Explain why the electromagnet loses its magnetic properties when the power supply is switched off, but the permanent bar magnet does not.
[1 mark]
Show mark scheme
Calculate — 2 marks
A steel screwdriver becomes temporarily magnetized when the north pole of a permanent magnet is stroked along its shaft several times. The screwdriver can now attract and hold steel screws. The weight of one steel screw is 0.3 N. The maximum magnetic force the temporarily magnetized screwdriver can exert is 1.5 N.
-
(01.1) Calculate the mass of one steel screw. Use g = 10 N/kg.
[1 mark]
-
(01.2) Calculate the maximum number of screws the temporarily magnetized screwdriver can hold vertically at one time.
[1 mark]
Show mark scheme
- (01.1) 0.3 ÷ 10 OR 0.3 / 10 = 0.03 kg (accept 30 g)
- (01.2) 1.5 ÷ 0.3 OR 1.5 / 0.3 = 5 (screws)
GCSE Perfect