Function of metal detector depends on. ?
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If you've ever made an electromagnet by wrapping a coil of wire around a nail and hooking it up to a battery, you'll know that magnetism and electricity are like an old married couple: whenever you find one, you'll always find the other, not very far away.
We put this idea to good practical use every minute of every day. Every time we use an electric appliance, we're relying on the close connection between electricity and magnetism. The electricity we use comes from power plants (or, increasingly, from renewable sources like wind turbines) and it's made by a generator, which is really just a big drum of copper wire. When the wire rotates at high speed through a magnetic field, electricity is "magically" generated inside it—and we can harness that power for our own ends. The electric appliances we use (in everything from washing machines to vacuum cleaners) contain electric motors that work in precisely the opposite way to generators: as electricity flows into them, it generates a changing magnetic field in a coil of wire that pushes against the field of a permanent magnet, and that's what makes the motor spin. (You can find out much more about this in our article on electric motors.)
In short, you can use electricity to make magnetism and magnetism to make electricity. A fantastically clever Scottish physicist named James Clerk Maxwell(1831–1879) summed all this up in the 1860s when he wrote out four deceptively simple mathematical formulas (now known as Maxwell's equations). One of them says that whenever there's a changing electric field, you get a changing magnetic field as well. Another says that when there's a changing magnetic field, you get a changing electric field. What Maxwell was really saying was that electricity and magnetism are two parts of the same thing: electromagnetism. Knowing that, we can understand exactly how metal detectors work.
We put this idea to good practical use every minute of every day. Every time we use an electric appliance, we're relying on the close connection between electricity and magnetism. The electricity we use comes from power plants (or, increasingly, from renewable sources like wind turbines) and it's made by a generator, which is really just a big drum of copper wire. When the wire rotates at high speed through a magnetic field, electricity is "magically" generated inside it—and we can harness that power for our own ends. The electric appliances we use (in everything from washing machines to vacuum cleaners) contain electric motors that work in precisely the opposite way to generators: as electricity flows into them, it generates a changing magnetic field in a coil of wire that pushes against the field of a permanent magnet, and that's what makes the motor spin. (You can find out much more about this in our article on electric motors.)
In short, you can use electricity to make magnetism and magnetism to make electricity. A fantastically clever Scottish physicist named James Clerk Maxwell(1831–1879) summed all this up in the 1860s when he wrote out four deceptively simple mathematical formulas (now known as Maxwell's equations). One of them says that whenever there's a changing electric field, you get a changing magnetic field as well. Another says that when there's a changing magnetic field, you get a changing electric field. What Maxwell was really saying was that electricity and magnetism are two parts of the same thing: electromagnetism. Knowing that, we can understand exactly how metal detectors work.
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