Lifting electromagnets and the Earth

The magnetic effect of current is at work all around you: in electromagnets, electric bells, motors, fans and loudspeakers. (Take apart an old phone speaker and it will stick to an iron cupboard: there's a magnet inside.)

Lifting electromagnets are strong electromagnets hung from cranes, like the one in Sumana's model. Picture a scrap yard: the operator lowers the magnet onto a heap, switches the current ON, and the iron and steel jump up and cling to it. The crane swings across, the operator switches OFF, the field disappears, and the load drops exactly where it is wanted.

That on-off switch is the whole point. A permanent magnet would never let go. Lifting electromagnets are used in factories and scrap yards to lift, move and sort heavy metal.

Now something much bigger. You learnt in Grade 6 that a hanging magnet always settles north–south, because the Earth itself behaves like a giant magnet. But why?

Deep inside the Earth, liquid iron moves in the core. That movement makes electric currents, and those currents make a magnetic field: the same link Oersted found, on the scale of a planet.

Many migratory birds, fish and other animals use this field to find their way across continents and oceans: it is their map. The Earth's magnetic field also acts as a shield, blocking harmful particles from space and helping to protect life.

In higher classes you will learn the reverse too: just as electricity can make magnetism, a moving magnet can make an electric current. That link is behind electric motors and power generators.