An electromagnet is a device that has the property of acquiring magnetic properties when an electric current passes through its coil..
Making a homemade one is very simple as we will see now. You just need an enameled copper wire and something like a core or body, something ferromagnetic like a screw or a piece of iron.
We can differentiate materials into three types: ferromagnetic, paramagnetic and diamagnetic depending on how they behave when magnetized.
It's a experiment so simple that it is ideal to do with children and introduce them to the world of science and technology.
How is this made
Its manufacture is very simple, we just have to wind a copper wire with insulation on an iron core, for example a screw. And connect it to a power source.
In general, ferrous materials are good for building electromagnets, if you take a magnet and stick it you can use it to build your electromagnet.
In the image above you can see the starting materials I was planning to use. A 9V battery, two screws to make 2 electromagnets and copper taken from the recycling an old monitor.
Remember that the copper wire that is used has to be enameled to isolate it and to be able to make the connections later we have to sand or scratch the terminals, the end of the cable. If not, it will not conduct current.
It may interest you: history of electrostatics and construction of a homopolar motor.
And the second electromagnet I have made with an Allen key, and it works much better than with the screw due to the type of steel with which it is made.
We can see how it works perfectly.
Uses and applications of electromagnets
Today they are used in a large number of devices, their use is very widespread.
- Electrobrakes or electric motor brakes
- Solenoid valves
- magnetic separators
At a home or DIY level, it can be used for all kinds of locks, homemade relays and switches.
Solenoid comes from the Greek and means "like a pipe"
History of electromagnetism and electromagnets
In 1820, the Danish physicist Hans Christian Orsted discovered that if you put a magnetized compass needle near a wire carrying current, it moved and became perpendicular.
Orsted did not investigate further. The one who did was André-Marie Ampère.
Ampere took Oersted's experiment and changed its polarity to find that the magnetized needle moved in the opposite direction. While experimenting to give it more intensity, he created the solenoids or electric coils.
He discovered that the coils behave like magnets attracting or repelling the magnetized needle.
In a second experiment, he placed two wires in parallel, one fixed and the other that could move freely, and saw how when current passed in the same direction they attracted each other, while if current circulated in different directions they repelled. So you could clearly see the force being exerted that there was a north pole and a south pole.
He empirically demonstrated several things:
- That the attraction exerted by a coil increased proportionally with the number of turns.
- and that it also increased with the intensity of the current.
That same year the French physicist François Arago showed that if a current passed through a copper wire, it could attract iron filings as easily as a steel urine magnet.
And the German physicist Johann Salomo Christoph Schweigger found that the deflection of the needle in Orsted's experiment could be used to measure the strength of the current and the first galvanometer was built.
The first electromagnet
In 1823, the English physicist William Sturgeon placed an iron bar inside a solenoid with eighteen turns. And he observed that the iron seemed to concentrate and strengthen the magnetic field. Sturgeon varnished the iron bar to protect it from short circuits, it was shaped like a horseshoe and could lift 4kg which was twenty times its own weight.
In 1830 Joseph Henry, an American physicist, improved the electromagnet. Henry insulated the wire of the loops instead of the iron core, in this way there could be many more loops and touch each other without producing short circuits. They are already the electromagnets we know today.
In 1831, using the current of an ordinary battery, he managed to lift a ton of iron with an electromagnet.
- Electromagnets. Easy calculation of single-phase and three-phase electromagnets. Manuel Alvarez Pulido
- Physics lessons. Volume III. Joseph Louis Manglano
- History and chronology of science and discovery. Isaac Asimov
1 comment on “How to make an electromagnet”
Inquiry: I was thinking of getting or making one for an automatic device that would move a very light lid. But the question is about the usage time. I would need the lid to open as follows:
– 3 intervals of 1 minute per day
– 1 interval of 2 hours per day
This second case is the one that worries me. Is there a cheap or homemade electromagnet that supports 2 h of current walking through it? How safe would it be to do so?