A hot plate produces heat by using electricity, instead of traditional means of producing heat by using fire. How it does this is by running electricity through its heat coils. The heat coils have a relatively high level of electrical resistance. As electricity encounters resistance along its course, the buildup changes from electrical energy, to heat energy, causing the heating coils to emit heat. So how does a hot plate produce heat? Remember, it is the resistance as the electricity moves through the coils.
The process, often referred to as Joule Heating, can be calculated with an equation. The heat energy that will be given off is equal to the electrical current squared, times the resistance, times the period of time, or (Heat Energy)=(Current)^2 * (Resistance) * (period of time). Therefore, a hot plate that takes a higher electrical current, and has a higher resistance in its coils, is going to produce more heat. By turning the hot plate control knob, the current is controlled, allowing the user to have more or less heat.