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Resistance heating uses electric current to produce heat through a specially designed conductor, with the amount of heat generated dependent on the resistance and strength of the current. It is commonly used in domestic and industrial applications but can also cause damage if left unchecked. The most common form is a coil or helix with a nickel-chromium alloy wire on a heat-resistant insulator. Overloading can lead to equipment damage and electrical fires.
Resistance heating is a process in which thermal energy is produced by passing an electric current through a specially designed conductor. The resistance that the conductor offers to the flow of current causes an atomic-level reaction inside it, producing energy and releasing heat. This reaction is subject to a scientific relationship known as Joule’s first law which sees the amount of heat generated by the process as dependent on the balance between the resistance of the conductor and the strength of the current. Resistance heating is one of the most commonly used forms of heat generation and is found in a wide range of domestic and industrial applications. Resistance heating is a product of all circuits in which electric current meets resistance; while it has many beneficial uses, it can damage or destroy electrical equipment if left unchecked.
Anyone who has used a kettle, toaster or bar heater on a cold evening is familiar with resistance heating. The effects of resistance heating were first noticed in the mid-1800s by James Prescott Joule and the phenomenon quickly became the cornerstone of one of the most widely used forms of heating of all time. The basic principle of resistance heaters centers on the reaction caused when the flow of electrons of electric current encounters the ionic structure of the conductor. The resulting electron/ion collisions see some of the energy of the accelerated electrons released as thermal energy. If you increase the current flow or the resistance of the conductor, the amount of heat generated also increases.
Resistance heaters most commonly take the form of a specially designed coil or helix or resistive wire embedded in or wound onto a heat resistant insulating substrate. Most resistance heating elements are of this type with materials such as high alumina ceramic being the most common insulator. The most common metal combination in the manufacture of wire used in resistance heating is a nickel-chromium alloy. The average composition of these alloys varies between 60/16% respectively for general use and 80/20% for high-end conductors. Nickel Chromium Alloy 60 is the more widely used of the two and can withstand temperatures of 1850°F (1000°C) without sagging or warping.
While resistance heating is obviously beneficial, the phenomenon can have catastrophic effects if left unchecked. All electrical conductors generate heat to some extent; when circuits or equipment become overloaded, the heat generated can severely damage or even destroy an appliance. Electrical fires are also a common result of runaway resistance heating.
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