At a recycling centre, a mixture of steel cans and aluminium cans moves along a conveyor belt.
A large electromagnet with an iron core is held above the belt. When the electromagnet is switched on, the steel cans are lifted off the belt. When it is switched off, the steel cans drop into a container.
Explain why the steel cans are lifted off the belt but the aluminium cans are not.
Explain why the core of the electromagnet is made of iron rather than steel.
A worker suggests replacing the electromagnet with a large permanent magnet made of cobalt steel.
Evaluate this suggestion.