Wire-wound resistors are made with coils of resistance wire. Sometimes called power resistors, they are very accurate and heat stable. The resistance value is marked. ยท Carbon resistors are common in electronic systems. Carbon is mixed with binder; the more carbon, the lower the resistance
Stepped or tapped resistors have two or more fixed resistance values. The different resistances (carbon or wire) are connected to different terminals in a switch. As the switch is moved, different resistance values are placed in the circuit.
Three types of variable resistors are used: rheostats, potentiometers, and thermistors. RHEOSTAT, POTENTIOMETER, THERMISTOR, Both types of thermistors change resistance with increasing temperature (NTC, resistance goes down as temperature goes up; PTC, resistance goes up as temperature go up.)