By using insulated wire, he was able to place thousands of turns of wire on a single core. As a result, one of his electromagnets could support as much as kg 2, lbs of weight.
This was to have a popularizing effect on the use of electromagnets. This law states that, for any closed loop path, the sum of the length elements times the magnetic field in the direction of the length element is equal to the permeability times the electric current enclosed in the loop.
To concentrate the magnetic field in an electromagnet, the wire is wound into a coil many times, ensuring that the turns wire are side by side along the edge. The magnetic field generated by the turns of wire passes through the center of the coil, creating a strong magnetic field there. The side of the magnet that the field lines emerge from is defined to be the north pole.
However, much stronger magnetic fields can be produced if a ferromagnetic material i. These wires are also kept at cryogenic temperatures to ensure that electrical resistance is minimal. Such electromagnets can conduct much larger currents than ordinary wire, creating the strongest magnetic fields of any electromagnet, while also being cheaper to operate because of there being no energy loss. Today, there are countless applications for electromagnets, ranging from large-scale industrial machinery, to small-scale electronic components.
In addition, electromagnets are used extensively for the sake of conducting scientific research and experiments, especially where superconductivity and rapid acceleration is called for. The strength of the magnetic field around the solenoid can be increased by:. Car scrap-yards use huge electromagnets to lift heaps of crumpled iron and steel. Switch off the current and the object crashes to the ground. In the home, by far the most common use of electromagnets is in electric motors. Think of all of those bits of electrical equipment with some kind of electric motor: vacuum cleaners, refrigerators, washing machines, tumble driers, food blenders, fan ovens, microwaves, dish-washers, hair driers.
The list is a long one, and when you start thinking more widely about electric motors in cars, lawn-mowers and a whole host of industrial applications, it becomes obvious that this application of electromagnets is extensive and extremely important to our daily lives.
The question of how electric motors work builds on the basics of magnetism introduced here, and is usually worked on in later years. Electromagnetic door bells are make and break devices which work via an electromagnet.
There is one electric circuit containing two switches. One is a conventional push-button switch. With these atoms in motion, and all in the same direction, the magnetic field grows. The alignment of the atoms, small regions of magnetized atoms called domains , increases and decreases with the level of current, so by controlling the flow of electricity, you can control the strength of the magnet.
There comes a point of saturation when all of the domains are in alignment, which means adding additional current will not result in increased magnetism. By controlling the current, you can essentially turn the magnet on and off. When the current is turned off, the atoms return to their natural, random state and the rod loses its magnetism technically, it retains some magnetic properties but not much and not for very long.
With a run-of-the-mill permanent magnet, like the ones holding the family dog's picture to the refrigerator, the atoms are always aligned and the strength of the magnet is constant. Did you know that you can take away the sticking power of a permanent magnet by dropping it? The impact can actually cause the atoms to fall out of alignment. They can be magnetized again by rubbing a magnet on it. The electricity to power an electromagnet has to come from somewhere, right?
In the next section, we'll explore some of the ways these magnets get their juice. Since an electrical current is required to operate an electromagnet, where does it come from? The quick answer is that anything that produces a current can power an electromagnet. From the small AA batteries used in your TV remote to large, industrial power stations that pull electricity directly from a grid , if it stores and transfers electrons, then it can power an electromagnet. Let's start with a look at how household batteries function.
Most batteries have two easily identifiable poles, a positive and a negative. When the battery isn't in use, electrons collect at the negative pole.
When the batteries are inserted into a device, the two poles come into contact with the sensors in the device, closing the circuit and allowing electrons to flow freely between the poles.
In the case of your remote, the device is designed with a load , or exit point, for the energy stored in the battery [source: Grossman ]. The load puts the energy to use operating the remote control. If you were to simply connect a wire directly to each end of a battery with no load, the energy would quickly drain from the battery. While this is happening, the moving electrons also create a magnetic field.
If you take the batteries out of your remote, it will likely retain a small magnetic charge. You couldn't pick up a car with your remote, but maybe some small iron filings or even a paper clip.
On the other end of the spectrum is the Earth itself. By the definition we discussed earlier, an electromagnet is created when electrical currents flow around some ferromagnetic core.
The Earth's core is iron, and we know it has a north pole and a south pole. These aren't just geographical designations but actual opposing magnetic poles. The dynamo effect , a phenomenon that creates massive electrical currents in the iron thanks to the movement of liquid iron across the outer core, creates an electrical current. This current generates a magnetic charge, and this natural magnetism of the Earth is what makes a compass work. A compass always points north because the metal needle is attracted to the pull of the North Pole.
Clearly, there's a wide range of electromagnet applications between small, homemade science experiments and the Earth itself. So, where do these devices pop up in the real world? In the next section, we'll take a look at how our everyday lives are affected by electromagnetism. Many electromagnets have an advantage over permanent magnets because they can be easily turned on and off, and increasing or decreasing the amount of electricity flowing around the core can control their strength.
Modern technology relies heavily on electromagnets to store information using magnetic recording devices.
When you save data to a traditional computer hard drive , for example, tiny, magnetized pieces of metal are embedded onto a disk in a pattern specific to the saved information. This data started life as binary digital computer language 0s and 1s. When you retrieve this information, the pattern is converted into the original binary pattern and translated into a usable form.
So what makes this an electromagnet? The current running through the computer's circuitry magnetizes those tiny bits of metal. This is the same principle used in tape recorders, VCRs and other tape-based media and yes, some of you still own tape decks and VCRs.
This is why magnets can sometimes wreak havoc on the memories of these devices. You may use electromagnetism every day if you charge a phone or tablet wirelessly.
The charging pad creates a magnetic field. Your phone has an antenna that syncs with the charger, allowing a current to flow. As you may imagine, the electromagnetic coils inside devices like these are small, but larger coils can charge larger devices such as electric cars. Electromagnets When an electric current flows in a wire, it creates a magnetic field around the wire. A simple electromagnet You can make an electromagnet stronger by doing these things: wrapping the coil around a piece of iron such as an iron nail adding more turns to the coil increasing the current flowing through the coil There is a limit to how much current can be passed safely through the wire because the resistance of the wire causes heating.
An electromagnet being used in a scrapyard.
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