How to make a permanent magnet

Q: How is a permanent magnet made?

Permanent magnets are made from hard ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize.

Electromagnet

Índice Show

What Is Magnetism?
Ways to Make a Magnet
Making Your Own Magnet
Increasing the Strength
How is a permanent magnet made?
What are three ways to make a permanent magnet?
What material can make permanent magnet?
How do you make a super strong permanent magnet?

Electricity and Magnetism

Practical Activity for 14-16

Class practical

Using a current-carrying coil of wire to make a permanent magnet from a steel rod.

Apparatus and Materials

Copper wire, PVC-covered, 150 cm with bare ends
Rod, hard steel
Iron filings in a pepper pot
Tintacks or paper clips, supply of
De-magnetizing coil (300 turns or 2400 turns)
Transformer or low-voltage AC supply
Power supply, low-voltage

Health & Safety and Technical Notes

Read our standard health & safety guidance

The steel rod may be a knitting needle or a piece of clock spring. As a poor substitute, short pieces of thick piano wire can be used.

Make sure the hard steel samples are not magnetized. If any are, de-magnetize them by passing them slowly through a coil carrying AC: for the 300-turn coil, use about 6 V AC: for the 2,400-turn coil, use about 20 V AC.

Procedure

Use iron filings or a plotting compass to check that the steel rod is not magnetised before proceeding
Wind a few dozen turns of insulated wire around the steel rod. (Leave enough wire free at either end to make connections to the power supply.)
Connect the ends of the wire to the low-voltage DC power supply, so that a large current flows round the coil.
Switch off the current. Test the steel rod again to see if it has become magnetised.
Determine where the rod's magnetic poles are.
Devise a method for magnetising the rod in the other direction.

Teaching Notes

How Science Works Extension: Students can make a magnet (by this method, or by the stroking method) and then test its strength. This requires them to devise and evaluate an approach to measuring the strength of a magnet. Here are some suggestions:

Find how many pins, tacks or paper clips will hang end-to-end from the magnet.
Lay a pin on the table. Gradually bring the magnet towards it. Measure the distance at which the pin starts to move.
Place a plotting compass on the table. Bring the magnet towards it from the side (east or west). Measure the distance at which the compass needle points at 45° to its original direction.

Students should be able to think of other ideas. By trying out several, they can evaluate the sensitivity of each.

This experiment was safety-checked in July 2007

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Other resources onElectromagnet

All the possible ways to make a permanent magnet are listed in Joseph Henry's student notebook, which is kept at Princeton University. Henry, the 18th century American physicist, is known – together with Michael Faraday – as the father of electrical technology, so it's no surprise that one of the methods he describes uses electricity. It turns out that if you have the right type of metal rod and enough electrical power, electromagnetic induction can turn the rod into a strong permanent magnet. How strong? Definitely stronger than a fridge magnet.

What Is Magnetism?

Magnetism and electricity are not only related, they are two sides of the same coin, and it was the phenomenon of electromagnetic inductance, discovered independently by Henry and Faraday, that led to this realization. Electrons have spin, which gives each atom a small magnetic field. It's possible to induce the electrons inside certain metals to spin in the same direction, and that gives the metal magnetic properties. The list of metals that do this isn't long, but iron is one of them and, because steel is made from iron, it can also be magnetized.

Ways to Make a Magnet

Among the methods Henry mentions for turning an ordinary iron or steel rod into a magnet are:

Rub the rod with a piece of metal that is already magnetized.
Rub the rod with two magnets, drawing the north pole of one magnet from the center of the rod to one end while you draw the south pole of the other magnet in the opposite direction.
Hang the bar vertically and hit it repeatedly with a hammer. The magnetizing effect is stronger if you heat the rod.
Induce a magnetic field with an electric current.

The end result of each method is to induce the electrons in the rod to spin in the same direction. Since electricity is made of electrons, it's a good assumption that the last method is the most efficient.

Making Your Own Magnet

You need a rod made of steel, iron or some other material that can be magnetized. (Hint: There aren't many other choices.) A 10d or larger steel nail is perfect. If you aren't sure it's steel, use a small magnet to test it. You also need a foot or two of insulated copper wire and a power source, such as a D-cell battery or a low-voltage transformer that you can plug into an outlet. If you opt for a transformer, be sure it has terminals to which you can connect wires.

To magnetize the nail, wrap the wire around it, forming as many coils as you can. It's fine to overlap the wire on top of coils you've already wound. The strength of the inductive field – and your magnet – increases as you increase the number of coils, so be generous. Leave the ends of the wires free, and strip off an inch of insulation so you can connect them to the power source.

Hook up the wires to the power source and turn on the power. Leave the power on for a minute or so and then turn it off. Test the nail by holding it over some iron filings. It should now be magnetized and attract the filings, even when the power is off.

Increasing the Strength

You can increase the strength of the magnet by increasing the number of coils. For example, if you double the number of coils, you double the strength of the inductive field. However, when you increase the wire length to do this, you increase the electrical resistance, which lowers the amount of current flowing through the wire. Since current, which is the movement of electrons, creates the field, the inductive power goes down. Offset this current loss by increasing the voltage, either by changing the setting on the transformer or by using a larger battery.

Warnings

Be sure to keep the voltage within safe limits. You don't want to electrocute yourself, nor do you want to create a magnet that sticks permanently to the refrigerator.

How is a permanent magnet made?

Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a strong magnetic field during manufacture to align their internal microcrystalline structure, making them very hard to demagnetize.

What are three ways to make a permanent magnet?

Magnets are made by exposing ferromagnetic metals like iron and nickel to magnetic fields. There are three methods of making magnets: (1) Single touch method (2) Double touch method (3) Using electric current.

What material can make permanent magnet?

Permanent magnets are made from special alloys (ferromagnetic materials) such as iron, nickel and cobalt, several alloys of rare-earth metals and minerals such as lodestone.

How do you make a super strong permanent magnet?

Rub the rod with two magnets, drawing the north pole of one magnet from the center of the rod to one end while you draw the south pole of the other magnet in the opposite direction. Hang the bar vertically and hit it repeatedly with a hammer. The magnetizing effect is stronger if you heat the rod.