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 lower current in circuits: One of the most important and widespread use of a resistor in a circuit is to lower current in a circuit. Resistors decrease current by ohm's law, I=VR. Therefore, the greater the resistance in a circuit, the lower the current is. High currents can be very dangerous in circuits and can burn out and destroy electronic components. To counter this, resistors are placed in series with the sensitive electronic components to keep them from being destroyed by excess current.
Resistors are used in voltage divider circuits: Resistors in voltage divider circuits can divide voltage so that different parts of circuits receive different voltage values as needed. A voltage divider circuit divides voltage to various parts of a circuit based on the resistance values. Voltage is dropped across the resistors according to ohm's law, V=IR. So the greater the resistance value of a resistor, the greater the voltage which is dropped across it, while the lower the resistance, the less voltage is dropped across it.
Resistors are used to set the gain of op amps: If you can recall op amp circuits, a resistor, called a feedback resistor, is placed over the input and output of the op amp. This resistor along with the input resistor sets the gain of the op amp circuit, according to the formula, -RFRIN, for inverting op amps.