Six original Cambridge-style questions on magnetic materials: sorting magnetic from non-magnetic, the properties of soft iron and steel, and choosing the right material for a job.
From the list below, state which materials are magnetic and which are not.
iron, copper, steel, plastic, nickel, brass
Magnetic: iron, steel, nickel. ✓
Not magnetic: copper, plastic, brass. ✓
Compare soft iron and steel by stating, for each, how easily it is magnetised and whether it keeps its magnetism.
Soft iron: magnetised easily; loses its magnetism easily. ✓✓
Steel: magnetised with difficulty; keeps its magnetism. ✓✓
An electromagnet is made by winding a coil around a core. The electromagnet must release whatever it is holding the moment the current is switched off.
(a) State the best material for the core.
(b) Explain why that material is chosen.
(a) Soft iron. ✓
(b) It magnetises strongly while the current flows, and loses its magnetism as soon as the current stops, so the load is released. ✓✓
State the most suitable material, soft iron or steel, for each of the following, and give no explanation.
(a) A permanent bar magnet for a laboratory.
(b) The core of the electromagnet in an electric bell.
(a) Steel. ✓
(b) Soft iron. ✓
A student says, "A permanent magnet must be stronger than a temporary one, because it lasts longer." Explain why this reasoning is wrong.
Two identical coils are wound, one around a soft iron core and one around a steel core. The same current is passed through each for a short time and then switched off. Describe and explain the difference in the magnetism of the two cores after the current is switched off.
Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.