Resistor Marking Codes are widely used in electronics to indicate the resistive value of the following components. This is basically just the electronic version of resistor color code and two components.
These resistor symbols are widely used in variable resistors, potentiometers, variable capacitors, filters, RF circuits, etc.
Resistor symbols provide a much easier and accurate way of determining the resistance of a given resistor. It is easy to see why resistors are often marked with this symbol instead of a numerical value.
Most often, they will be included in schematics to denote value, resistance and dissipating power.
Also known as a stripe marker or triangle marking, the resistor symbol is one of the basic icons in electronics alongside rectangles, ovals and others.
A potentiometer or pot is a variable resistor with a third terminal called the wiper, on which a slider or movable contact moves.
The movement of the wiper along the resistance element forms a variable voltage divider that can give a steady output voltage independent of variations in resistance due to temperature, aging, or stress of parts.
The potentiometer was invented by Sigmund Graumann and was used in volume control systems before electrically controlled volume was widely available.
Before I get to the variable resistor symbol, let me describe what a resistor is. A resistor is defined as an electrical device which resists the flow of current through it, which in turn reduces voltage or current.
The resistor is constructed with a small length of wire that has been coated with a heavier metal that prevents electrons from flowing through it. It also has two ends that are used to connect to an electronic circuit.
Through the use of a small screwdriver or similar tool, a trimmer can be finely adjusted by rotating it so that any number of different resistances are achieved.
Trimmers are commonly used in place of potentiometers due to their ruggedness and reliability. Their main application is to allow precise adjustment of one or more parameters on equipment, including television receivers, radios, computers (to adjust the AC power supply voltage), and others.