Different Uses of Resistors
Resistors, either stand alone or used with other electronic components such as capacitors and inductors, have a wide variety of uses in circuits. We will go over some of the most common ways resistors are used in circuits.
Resistors are used in timing circuits: When resistors and capacitors or resistors and inductors are placed in a circuit together, in series or in parallel, they form an RC or RL timing network. The greater the value of the resistance, the longer the time it takes for a capacitor or inductor to charge up. Conversely, the lower the value of the resistance, the shorter the time charging takes. This is because the greater the resistance, the more it slows down current. So resistors are heavily used in timing circuits.
Resistors are used in filtering circuits: Passive components, capacitors and inductors are used with resistors to form low-pass and high-pass filters. The orientation or placement of the resistor in the circuit determines whether it acts as a high or low-pass filter. These serve as frequency filters in circuits; they allow a certain range of frequencies to pass through into the circuit and block all other frequency ranges. A low-pass filter is a filter which allows low frequencies to enter through. A high-pass filter is a filter which allows high frequencies to pass though, blocking low frequencies.
Special functions: Besides the basic types, other types of resistors exist with special functions. A varistor is a resistor which varies in values based on the voltage that drops across it. Thermistors are resistors which vary depended on the temperature they are exposed to. Potentiometers are resistors which can be varied to produce a range of different values which they are rated for. A photoresistor is a resistor which varies according to the amount of light that strikes its surface.