Film type resistors

Carbon, nichrome, or some mixture of ceramic and metal can be applied to a cylindrical form as a film, in order to obtain a desired value of resistance. This type of resistor is known as metal-film resistor. It looks like a carbon-composition type, but the technique of construction is totally different.

Figure--   Construction of a film type resistor.

The cylindrical form is made of the insulating substance, like porcelain. The film is deposited on this form by several methods, and the value tailored as required. Metal-film units can be made to have almost exact values. Film type resistors generally have low to medium-high resistance.

A major advantage of film type resistors is that they, like carbon-composition units, do not have much capacitance or inductance. A disadvantage of it in some applications is that they cannot handle as much power as the more massive carbon-composition units or as the wirewound types.