Engineering Feature Physics

Toasters on Books

Have you noticed the rise of toasters on the covers of pop science books lately? Believe it or not, there is a reason for the appliance’s popularity in the physics community, especially for the scientists trying to bring modern physics into the homes of laypeople. It illustrates a number of fundamental physics principles. Here are a couple, as described in Helen Czerski’s Storm in a Teacup*:

There’s a beautiful simplicity about what the toaster is up to. When you put the bread in place, it rests on a spring-loaded tray. The springs underneath are pushing the bread up to its “popped” position, high above the heating elements. But you’re strong enough to push the bread down in spite of those springs. And once the tray reaches the bottom of the toaster, a protruding bit of metal fills the gap in not one, but two circuits. One of those circuits deals with the heating, so electricity starts to flow around the toaster to heat the bread. But the other circuit is a lot more interesting. The electrons in that circuit shuffle along and around a section of wire that is wrapped around a small lump of iron. It’s a bit like a helter-skelter ride for electrons–they spiral around and around the iron and then out and along the rest of the circuit back to the plug socket. That’s all. But because magnetism and electricity are so deeply intertwined, when and electric current runs through a wire, it creates a magnetic field around that wire. Sending electrons around a coil of wire means that each time the electrons loop around, they’re adding to the same magnetic field. The iron core in the middle of the coil reinforces the magnetic field and makes it even stronger. This is an electromagnet. When an electric current is running through the wire, it’s a magnet. When the current stops, the magnetic field goes away. So when you push down the lever on the toaster, you’re switching on a magnetic field at the base of the toaster that wasn’t there before. Since the bottom of the bread tray is made of iron, it stocks to the magnet. In other words, while I’m poking about in the fridge, a temporary magnetic field is holding the bread tray in place. The toaster has a timer on the side, and the clock starts when the circuits are connected. When the time is up, the timer cuts the power to the whole toaster. Since there’s no power to the electromagnet, it stops being a magnet. Nothing is holding the bread down anymore, so the springs pop it up. I sometimes forget that I’ve unplugged the toaster, but I find out pretty quickly. If I try to push the lever down, it pops straight back up, even if I push it down all the way. That’s because there’s no power to the electromagnet, so it can’t hold the bread tray down. It’s such a simple system, and stunningly elegant.


*Storm in a Teacup: The Physics of Everyday Life (January 2017) does not have a toaster on the cover. Appropriately, it has a teacup.



Breakfast with Einstein: The Exotic Physics of Everyday Objects by Chad Orzel



Engineering and Technology magazine says, “For an entertaining reminder of how physics isn’t just about billion-dollar experiments like the Large Hadron Collider or extreme astrophysical environments like black holes, Breakfast with Einstein: The Exotic Physics of Everyday Objects shows how an ordinary morning routine depends on some of the weirdest phenomena ever discovered. Author Chad Orzel, also responsible for international bestseller ‘How to Teach Quantum Physics to Your Dog’, elevates the everyday by showing the phenomena that can be found in even the simplest activities. If you want to find out how the humble alarm clock holds secrets about quantum mechanics, or why classical physics couldn’t explain why your toaster’s heating element glows orange this is the place to start.” (December 2018)


The Toaster Project: Or a Heroic Attempt to Build a Simple Electric Appliance from Scratch by Thomas Thwaites


How can an appliance made from 404 pieces which themselves are comprised of 38 different materials mined from across the globe cost the consumer as little as $6.10? The Toaster Project is a deep dive into the complicated world of consumerism and economics told through the lens of a witty student trying to make a toaster from scratch. Not to spoil it or anything, but it winds up costing him $1,837.66 and nine months to make.

The book is both a silly adventure (Thwaites and his pal cross into dangerous mountainous Scottish territory with little equipment besides a pen that lights up and a map scribbled by a guy they found in a pub) as well as an attempt to see the world of consumer goods differently, not by the dollar amount on the price tag but by the ecological price our planet paid to make it affordable to you. (September 2011)


The Physics of Everyday Things: The Extraordinary Science Behind an Ordinary Day by James Kakalios


Physics professor, bestselling author, and dynamic storyteller James Kakalios reveals the mind-bending science behind the seemingly basic things that keep our daily lives running, from our smart phones and digital “clouds” to x-ray machines and hybrid vehicles. This book takes place over one day, from getting out of bed and making breakfast to getting to work and interacting with the engineering and technology that makes the modern world so modern. (May 2017)

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