A rectangular resistance coil is an electrical component used to introduce resistance into a circuit. The coil is made of a wire wound around a rectangular frame with a resistance value that can be varied by changing the number of turns of wire. The rectangular shape of the coil allows for a larger surface area, which can dissipate more heat, making it suitable for high power applications.

The coil is usually made of a material with high resistance, such as nichrome, and can be used for various applications, including circuit testing, calibration, and as a load resistor. The resistance value can be adjusted by sliding contact along the length of the coil, which changes the length of wire in the circuit, altering the resistance.