How a toaster works · OakCrest Academy

🍞 How a toaster works

Pressing the lever lowers the carriage and the bread, stretches a spring and, at the bottom, closes a switch, so that current flows.
The current passes through ribbons of nichrome wound on mica sheets. Their resistance turns electrical energy into heat: P = V² ÷ R, so 120 volts across 16 ohms gives 900 watts.
Within about half a minute the wires reach several hundred degrees Celsius and glow orange-red. They radiate infrared, which dries the bread's surface and then browns it through the Maillard reaction and caramelisation.
A timer, set by the browning dial, keeps an electromagnet switched on, and the magnet holds the carriage down. Energy delivered is power × time: 900 watts for 120 seconds is 108,000 joules, or 108 kilojoules.
When the time is up, the magnet releases the carriage; the spring pulls it up, the toast pops and the switch opens, cutting the power.

New words

resistance: how strongly a material opposes the flow of electric current; it is measured in ohms (Ω)
nichrome: an alloy (a mixture of metals) of nickel and chromium that resists current and survives being red-hot
mica: a natural mineral that splits into thin, heat-proof sheets and does not conduct electricity
infrared: radiation just beyond red light, invisible to us, that we feel as heat
electromagnet: a coil of wire that becomes a magnet only while current flows through it
Maillard reaction: the reaction between sugars and amino acids that browns toast, crusts and roasted food

🏠 Try it for real

With a grown-up, watch a toaster from above as it heats: note how many seconds pass before the wires begin to glow. Then read the power rating on its label and calculate the energy used for one round of toast with energy = power × time. Only a grown-up should touch the toaster; never put anything metal inside, and unplug it before cleaning.

💭 Talk about it

Explain it: in two to four sentences, explain why turning the browning dial makes darker toast, even though it does not make the wires any hotter. Then test a claim: a friend says 'the bread pops up because the toast gets too hot.' Is that true? What evidence from the figure supports or refutes it?

Now explain it back: point at each part and say what it does.