Different Types of Resistor Design

The word resistance has two meanings:

Generally this refers to the attribute of an electrical conductor to impede the flow of electrons and, as such, one speaks of the electrical resistance of a conductor. This meaning has already been elaborated on in the previous section of the course.

In certain components used in electrical engineering this conductor attribute is exploited. These components are referred to as resistors, components providing a well-defined resistance. These will be examined in the following course section.

The subsequent illustrations show the circuit symbols for different types of resistors.

Basic resistor	Variable resistor	Resistor with sliding contact (potentiometer)

Resistors come in all kinds of designs:

Film resistors consist fo a thin ceramic tube on which a thin layer of carbon, metal oxide or metal is applied. An insulating lacquered finish protects the resisting film. The resistance value is indicated by coloured rings (more information to follow).
For low  resistance values (e.g.  0.1 W) and higher currents we use wire resistors. These consist of insulating bodies containing a winding made of resistive wire.
Variable resistors (potentiometers, trimmers) have a sliding contact, with which variable lengths of the resistance material (e.g. wire or carbon) can be introduced into the circuit. This is how desired voltage and current levels can be set precisely.