What is a resistor?

 
What is a resistor?

The resistor is a passive electrical component to create resistance in the flow of electric current. In almost all electrical networks and electronic circuits they can be found. The resistance is measured in ohms. An ohm is the resistance that occurs when a current of one ampere passes through a resistor with a one volt drop across its terminals. The current is proportional to the voltage across the terminal ends. This ratio is  represented by Ohm’s law: Resistors are used for many purposes. A few examples include delimit electric current, voltage division, heat generation, matching and loading circuits, control gain, and fix time constants. They are commercially available with resistance values over a range of more than nine orders of magnitude. They can be used to as electric brakes to dissipate kinetic energy from trains, or be smaller than a square millimeter for electronics. Resistor definition and symbol A resistor is a passive electrical component with the primary function to limit the flow of electric current. The international IEC symbol is a rectangular shape. In the USA the ANSI standard is very common, this is a zigzag line (shown on the right). Overview of types and materials Resistors can be divided in construction type as well as resistance material. The following breakdown for the type can be made: Fixed resistors Variable resistors, such as the: Potentiometer Rheostat Trimpot Resistance dependent on a physical quantity: Thermistors (NTC  and PTC) as a result of temperature change Photo resistor (LDR)  as a result of a changing light level Varistor (VDR)  as a result of a changing voltage Magneto resistor (MDR) as a result of a changing magnetic field Strain Gauges as a result of mechanical load For each of these types a standard symbol exists. Another breakdown based on the material and manufacturing [… read more]