At first glance, a toaster seems simple. After all, its only function is to toast foods like bread and waffles. But a toaster is really an electronic device. It uses electronic components like capacitors, microchips and even an electromagnet.

To make toast, you put bread in the toaster and press a lever. The lever connects to a metal plate. Attached to the plate are a plastic wedge, a metal bar, a spring and the trays that hold the bread.

The wedge forces strips of metal to touch contacts on a printed circuit board (PCB). This completes a circuit. Electricity flows through nichrome wires wrapped around mica plates. The wires heat up due to electrical resistance. They warm the plates, and the plates toast your bread.

When you press the lever, the metal bar touches an electromagnet. This electromagnet holds the bar, the trays and the lever in the down position until the circuit breaks. Then, the magnet lets go, and the spring pulls the plate to the up position.

A second PCB controls how long it takes for the circuit to break. It uses wires, resistors and microchips to send instructions from the toaster’s controls to the electronics inside. When you push a button, it presses a switch on the PCB. A light-emitting diode (LED) next to the button lights up, and the PCB changes how current flows through the toaster.

You can also turn a dial connected to a variable resistor to adjust how dark your toast will be. The resistor affects how quickly current travels to a capacitor, which stores electricity and acts like a timer. Once the capacitor stores a certain amount of electricity, it breaks the circuit that powers the electromagnet and the wires. Your toast pops up, and the mica plates cool off. The more resistance the current encounters, the longer it takes the capacitor to fill. The longer it takes to fill, the darker your toast will be.