In a toaster, the resistor, or the heating element, is typically located inside the toaster's slots, where the bread is inserted for toasting. The heating element is responsible for generating the heat needed to toast the bread.
The heating element in a toaster is made of a high-resistance material, usually nichrome wire, which has a high electrical resistance and can generate a significant amount of heat when electricity passes through it. When you turn on the toaster and set it to a specific toasting level, electricity flows through the heating element, and the resistance in the wire causes it to heat up.
As the heating element heats up, it radiates infrared radiation that directly heats the surface of the bread, initiating the toasting process. The heat generated by the resistor causes the Maillard reaction, as explained in the previous answer, leading to the browning of the bread and the transformation of the starches and sugars in the bread into a toasted and flavorful product.
It's worth noting that the exact design and location of the heating element may vary depending on the toaster's model and manufacturer. In some toasters, the heating element may be visible inside the slots, while in others, it may be enclosed or covered for safety reasons. Regardless of the specific design, the heating element (resistor) is a critical component of a toaster and responsible for the toasting process.