4.3 Lifting Magnets & a Magnetic Earth
The most spectacular use of the magnetic effect is the lifting electromagnet — Sumana’s model, scaled up to industrial size.
Magnets That Pick Up Cars A lifting electromagnet is a strong electromagnet hung from a crane. The operator just switches the current ON to grab heavy iron and steel objects, and OFF to release them — the magnetic field appears and disappears on command. In factories and scrapyards, these magnets move, lift and sort heavy metal far faster than any hook could. The huge advantage of an electromagnet over a permanent magnet is exactly this: you can turn it off.
Worked Example
Why is a lifting electromagnet better than a permanent magnet for a scrapyard crane?
A permanent magnet is always magnetic — once it grabs a load of scrap, how would you make it let go? An electromagnet is magnetic only while current flows: switch it on to lift, off to drop. That on/off control is precisely what sorting and moving metal needs. (It can also be made far stronger, by adding cells, turns and an iron core.)
Why is the Earth itself a magnet?
A Step Further: Our Magnetic Planet A freely suspended magnet always settles pointing north–south because the Earth itself behaves like a giant magnet. But why? Deep in the Earth’s core, molten iron moves, creating electric currents — and, just as in Oersted’s wire, those currents generate a magnetic field. So the same principle that powers a toy electromagnet runs the entire planet’s magnetism. Migratory birds, fish and other animals use this field to navigate, and it acts as a shield that blocks harmful particles from space, protecting life on Earth.
The Deeper Link You have seen that electricity produces magnetism. In higher grades you will meet the astonishing other half of the story: a moving magnet can produce electricity. This two-way bond between electricity and magnetism is the basis of both electric motors (electricity → motion) and power generators (motion → electricity) — the machines that run the modern world.