Tag Archives: Electromagnet

How Does a Speaker Work?

It’s easy to look at a piece of technology (like a speaker) and feel like you’re looking at a black box, wondering how they work. What’s hidden inside them? It must be complicated, right? Often times, that holds some truth. But you would be surprised how far you can get if you can nail down just a key concept or two. To understand how something like a speaker works, the inherent link between electricity and magnetism is one of those concepts. 

This link between electricity and magnetism is most often used by creating one from the other. Magnetic fields can create (or induce) electric fields. For example, our hand crank motor moves a wire around a magnet, and this changing magnetic field induces an electric field, which we can use as electricity, to do something like light up a lightbulb. The phenomenon of inducing an electric field from a magnetic field has given a straightforward name of electromagnetic induction.

motor

 And, lucky for us, induction goes both ways: electric fields can also induce magnetic fields! We have an electromagnet at camp that turns a screw into a magnet. Around the screw is a coil of wire, and pressing the button allows electric current (from the outlet) to flow through the coils that, and that electric current induces a magnetic field– creating a temporary magnet out of the screw.

electromagnet 

Inside a speaker, you’ll also find a type of electromagnet… using coils of wire wrapped around a permanent magnet. Pulses of electricity carry sound information from your phone down through the coils of the electromagnet, rapidly changing the direction of the magnet’s magnetic field back and forth, which creates alternating magnetic forces, and these forces are what moves your speaker cone back and forth, AKA creating sound! 

To create your own speaker, you need a 2 to 3 strong magnets, enamel wire (copper wire with a thin insulated coating), and something cone-shaped to funnel the sound. We used a phone to play music, and opted to use an aux cord and alligator clips to connect the copper wire to the headphone jack. Make sure to use the 1st and 3rd section of the aux cord. (You can also sacrifice a headphone jack and wrap the exposed wires around the two ends of the copper wire.)  When using the enameled wire, you need to sand the ends of the wires down so that the copper wire is showing. (You won’t get a connection if you don’t). Wrap the wire around the magnet (the more turns, the better the results!) and use another magnet on the other side of your sound funnel/speaker (we used a bowl). This magnet helps the speaker work better, and has the added result of keeping your magnets easily attached to the speaker. When you put these all together, you should have a speaker! 

Tip: The speaker works off induction, and the more you have of it, the better results you’ll get. To increase induction, you can increase how many turns and how big the coil of wire is, and you can increase the strength of magnets. 

speaker full setup close

Electricity and magnetism are complicated subjects to study, but you don’t need years of studying to take advantage of it. By knowing the idea of electromagnetic induction, you now know how a simple motor is made, and can make one too [https://astrocampschool.org/homopolar-motorcar/] ! From speakers, to washing machines, to windmills, the power of wires + magnets basically endless, and integral to our way of life! In a world surrounded by motors and electromagnets, you’ll never look at your world the same way.

What is an Electromagnet?

Here at AstroCamp, one of our most popular classes is Electricity and Magnetism. At first glance, it might not be obvious how these things are related, but they are actually tied together through important physical principles.

To give you some evidence, let me introduce the electromagnet.

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This is really just a metal rod wrapped with a bunch of wire. Without any electricity going through the wire, it doesn’t do anything special. Now, let’s press the button and let electricity flow through the coil!

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What is going on? Well, to explain that we have to back up a bit. Let’s start by answering this question: What is electricity? It is the thing that runs our light bulbs, smart phones, computers, and air conditioning but what is it on a more fundamental level? What is happening?

asset-v1-pkuhighschoolph1019999_t1typeassetblockatom-light-640x360As you probably know, everything you have ever touched is made out of atoms, and these atoms have three parts: the positively charged proton, the negatively charged electron, and the neutral neutron. These charges determine how the particles interact; particles with identical charges push away while those with opposites attract.

Electricity, as you may have figured out by looking at the word, has to do with electrons. Electricity basically means moving electrons. However, physics has a bit of a surprise for us here. Whenever a charge is moving, it makes a magnetic field–if this word seems confusing, this is just what is produced by a magnet to push and pull on other magnets–around it in a circle. This happens every single time. You might be tempted to ask why, but I don’t have a great answer for you. This is just how nature is.

All we have done to make an electromagnet is sort of durn this trick on its head. By wrapping the wire into a coil, the circular magnetic field created every time an electron moves adds up in the middle. This kind of design is called a solenoid.

what-is-a-solenoid-and-solenoid-magnetic-field

This awesome illustration shows how the circular magnetic fields around each wire add up in a solenoid to make a strong magnetic field inside. All credit goes to Paul Nylander.

This might seem like a simple lab trick to convince you about the mysterious but very real connection between electricity and magnetism, but it turns out to be an incredibly useful and important design. Outside the obvious purpose of picking things up like the giant electromagnets at junkyards, electromagnets are used in speakers, hard drives, MRI machines, motors, generators, and many other things you might not expect!

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This is a view inside the Large Hadron Collider at CERN, the most powerful particle accelerator on the planet! This shoots tiny particles at very near the speed of light along a very precise track. While you might expect it to be the metal walls that keep the particles inside, the tiny particles would actually fly right out through the walls! So how do they keep those pesky particles in line? They steer them using incredible powerful superconducting ELECTROMAGNETS! Photo credit CERN.

Written By: Scott Alton

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