Resistors

Resistors are electrical components that resist the flow of current through a circuit. Many electrical components are resistors, and some even change their resistance level based on electrical or non-electrical factors. Because resistors can be used to reduce the amperage in a circuit, it can be used to protect other components in the circuit, or reduce the effect of power passing through the component in series with it. For example, a resistor in series with a light bulb reduces the amperage of the circuit, which reduces how quickly a battery powering the bulb drains, but also reduces the light output of the bulb.

Variable Resistors

Variable resistors are a category of resistor that has its resistance changed by factors such as heat, mechanical movement, or other factors that can be chosen to make a particular kind of sensor. As the resistor's value changes, a computer that can gather information based on that change.

Thermistors

Thermistors change their resistance as their temperature changes. There are two types of thermistors, negative temperature coefficient (NTC) thermistors, which decrease their resistance as temperature rises, and positive temperature coefficient (PTC) thermistors, which increase their resistance as temperature rises. Most thermistors in automotive applications are of the NTC variety. Common uses for these sensors are in coolant temperature sensors, air charge temperature sensors.

Potentiometers

Potentiometers are varible resistors that are typically a resistor component that doesn't actually change, but instead has a contact that moves across the resistor material. A common use for this type of variable resistor is in throttle position sensors and fuel level sensors.

Rheostats

Rheostats are potentiometers that have two terminal connections.