Though most of us don’t realise it, we encounter electromagnets every day. They’re a means of both translating kinetic energy into electrical energy, and of the reverse. Let’s examine some of the places we might find one.
In order to reproduce music in your home or car, a set of speakers pushes air back and forth. We then perceive these changes in air pressure as sound. This is done by building an electromagnet into the back of a cone, which is what actually pushes the air. When a signal passes through the electromagnetic driver, the corresponding sound in produced. A microphone makes use of just the same arrangement – vibrations in the air move an electromagnetic ribbon, which translates those vibrations into sound.
Magnetic Resonance Imagining provides modern doctors with a non-invasive means of examining the interior of a human body. If there’s something wrong with your internal organs, then the chances are that you’ll be subject to an MRI scan. This procedure has allowed potentially very serious conditions to be identified very early on, and thus it’s helped to slash mortality rates across the world.
So how does an MRI scanner work? Let’s think about what the human body is mostly made from: water. Water is built from two elements: oxygen and hydrogen. Each hydrogen atom comes with just a single positively-charged proton at the core and a negatively charged electron zipping around the outside. Under a magnetic field, each of these protons will be aligned in the same direction, and then when the field is deactivated, they’ll emit radio energy as they return to their original positions. By rapidly turning the field off and then on again, the MRI scanner can build an image of the inside of any object – provided, of course, that it’s not a block of metal.
In order to plumb the deepest mysteries of the universe, scientists must expose particles to very peculiar conditions. Among these is moving particles to incredible speeds – often somewhere near the speed of light. To do this, large electromagnets are arranged in a ring, each of them alternately pushing and pulling the particle as it travels around the loop, getting faster and faster until it reaches the desired speed.
An induction hob doesn’t contain a heating element – it instead directly produces heat within the pans on top of it. The magnets in the induction hob move the particles inside the pan very quickly, and this generates the heat which allows you to cook. This arrangement means that you’ll be able to touch the work surface while the hob is on – but naturally, you should avoid doing so after you’ve had a hot pan on the hob. They tend to be safer and more energy efficient than more traditional designs, and they’re proving increasingly popular.
An internal combustion must be turned in order to start. Without this step, it won’t be able to draw oxygen into the cylinders, and thus the combustion process won’t begin. Most modern cars require a electric starter motor in order to perform this job. It draws power from the car’s battery, and connects to the engine’s flywheel via a retractable gear called a pinion.
Electromagnets feature heavily in a starter motor. They’re used to make the motor spin, for one thing, and they’re also used to complete the circuit that activates the motor. Starter motors draw a high current, and thus manually completing the circuit would cause dangerous arcing as the two contacts approached one another. In order to prevent this, the circuit is instead completed by a solenoid electromagnet on a separate, low-current circuit. The solenoid is spring-loaded, and snaps in and out of place too quickly for the air around the spark to be heated. You’ll find BMW, Ford and Vauxhall starter motors available online, along with those to fit a range of other vehicles.
Another important electrical component in your car is the generator, which uses the motion of the car’s wheels to charge the onboard battery. It does this by fixing a rotating magnet within a set of coils. As the wheels spin, the magnet rotates, and thus a charge is produced in the coils thanks to induction. Generators come in two forms – older cars contain inductors, while newer ones contain alternators. The latter are more lightweight, but they put out an alternating current, which must be translated into a direct one via a small device called a rectifier.