Sky Division 2 Marine Science Electricity Project June 1, 2020

How Toasters Work: ● Toasters toast bread using infrared radiation, which is produced by the coils inside a toaster. ● The most common way for toasters to produce infrared radiation is with nichrome wire (wire made out of nickel and chromium) wrapped across a mica sheet (a kind of mineral) ● Nichrome wire has a high resistance which allows a short length of it to get very hot, and it doesn’t rust ● Toasters are also equipped with a spring loaded tray that pops the bread up, and a timer that releases the tray when the bread is done toasting ● Most toasters have two bread slots, with two mica/nichrome wire sheets on each side of a slot ● Each side also has two grates that hold the bread in place, and a metal part at the bottom that pushes the bread up or down ● When the holder nears the bottom of the slot the two grates close together, and the whole thing is controlled by the spring loaded tray, or the handle on the outside of the toaster ● Three things need to happen when you push the handle down ○ Something needs to hold down the handle until the bread is done toasting ○ Power needs to run through the nichrome wires ○ The timer needs to release the spring loaded tray, or handle, at the right time ● When you push down the handle, a plastic bar inside the toaster connects with two copper contacts which supply power to the wires, and a metal tab connects with an electromagnet that holds the bread down To Recap: ● When the handle of a toaster is pushed down, a plastic bar connects with the contacts ● In most toasters, about 120 volts run through the contacts to the wires ● The circuit inside a toaster is made up of ​resistors, capacitors, and transistors, which power the electromagnet ● A metal tab on the handle of the coaster is attracted to the electromagnet, which holds the bread down ● The toast pops up when the timer goes off ● The timer is controlled by a capacitor, which charges through a resistor, and when the capacitor reaches a specific voltage the power flowing to the electromagnet is cut off, which releases the spring and the bread pops up ● The dial with how toasty you want your bread is controlled by something called a variable resistor, and changing the resistance changes how long it takes the capacitor to charge, which changes how long it is before the timer goes off and the toast pops up.

Source:​ ​https://home.howstuffworks.com/toaster4.htm

My Toaster Circuit:

Sky Waddell-Brittle Division 2 Marine Science Electricity Project Write Up June 1, 2020

Our final unit in MST this year has been focused on electricity. We’ve learned about electrons, and how they travel through circuits, and we’ve built our own circuits while doing labs. Some definitions we discussed in class, and are important to know are: current - “​a flow of electric charge”​, voltage - “​electric potential or potential difference expressed in volts”​, and resistance - “​the power or capacity to resist”​. For our final project, we each had to choose an electrical appliance, draw a circuit diagram for it, and explain how it worked. I chose a toaster, and will be explaining the circuitry and mechanics that make toasters function. The first step in understanding how toasters work, is looking at all of the components inside. Toasters toast bread using infrared radiation, which is produced by the coils inside a toaster. The most common way for toasters to produce infrared radiation is with nichrome wire (wire made out of nickel and chromium) wrapped across a mica sheet (which is a kind of mineral.) Nichrome wire has a high resistance which allows a short length of it to get very hot, and it doesn’t rust even when exposed to high heat. Toasters are also equipped with a spring loaded tray that pops the bread up, and a timer that releases the tray when the bread is done toasting. Most toasters have two bread slots, with two mica and nichrome wire sheets on each side of a slot. Each side also has two grates that hold the bread in place, and a metal part at the bottom that pushes the bread up and down. When the handle of a toaster is pushed down, the holder lowers inside the toaster, and when it nears the bottom of the slot the two side grates close together, holding the bread in place. Then the bread toasts and pops back up. But how does the toaster know how long to toast the bread for? And how does it pop back up? That’s where the circuitry comes in. Three things need to happen when you push the handle on a toaster down. First, something needs to hold down the handle until the bread is done toasting, second, power needs to run through the nichrome wires, and third, the timer needs to release the spring loaded tray, or handle, at the right time. When you push down the handle, a plastic bar inside the toaster connects with two copper contacts which supply power (usually around 120 volts) to the wires, and a metal tab connects with an electromagnet that holds the bread down. The electromagnet is controlled by a number of ​resistors (an electrical component which resists a certain amount of current flow through a circuit,) capacitors (which hold and store current,) and transistors, (which can either amplify current or act as a switch.) A timer controls how long the bread is kept in the toaster, and the timer is controlled by a capacitor. The capacitor is charged through a resistor, and when the capacitor reaches a certain voltage, it cuts off the power flowing to the electromagnet. This releases the spring loaded tray, and the toast pops up. Now you may be wondering how the timer knows when to go off. The timer is controlled by the resistor, more specifically a variable resistor. You can change the resistance of the resistor, by changing the level of toastiness on the outside of the toaster. Changing the resistance changes the amount of time the capacitor has to charge for, which allows the bread to pop up at any level of toastiness that you want. And voila, that is how a toaster works! When starting this project I was scared that it would be very confusing and difficult, but the entire learning process was less daunting than I thought it would be, and actually very fun and informative!

Electricity Graphs