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A resistor is a passive double-ended electrical component. After connecting to the circuit, the resistance is fixed and can limit the current through the branch connected to it. On the one hand, the resistance that cannot be changed is called a fixed resistor. On the other hand, the resistance of a potentiometer or variable resistor is variable. The main physical characteristic of a resistor is to convert electrical energy into heat. It can also be said that it is an energy-consuming component, because the internal energy is generated when current passes through it.


The role of resistors

In short, the role of resistance is to limit current, shunt, and divide voltage, and convert electrical energy into internal energy (heating) in the circuit. According to Ohm’s law, through calculation, parallel and series resistors can be used to achieve the required current and voltage. In addition, there are different combinations of resistors and switches to produce voice switches, photosensitive switches, infrared switches, etc.

  1. Limit current: In order to prevent the components connected in series from being burned out by excessive current and to ensure the normal operation of electrical appliances, variable resistors can usually be connected in series in the circuit.
  1. Current shunt: The resistor is connected in parallel with the component or circuit that needs to be shunted, and the voltage does not change. The purpose of this resistor is to shunt current.
  1. Voltage shunt: Generally speaking, electrical appliances are marked with a rated voltage value. If the power source is higher than this value, the electrical equipment cannot be directly connected to the power source for normal operation. In this case, a resistor with an appropriate resistance can be connected in series in the circuit to share a part of the voltage, so the appliance can work at the rated voltage. At this time, the role of the resistor is to divide the voltage.
  1. Provide bias voltage: In a transistor circuit, the resistor is connected between its base and the operating voltage. At this time, the power supply provides a bias voltage to the base through a resistor, and the resistor can determine the bias voltage. The role of the resistor in the circuit at this time is to provide a bias voltage.
  1. Negative feedback: Used in the resistance between the base and collector of the transistor, the feedback branch of the negative feedback circuit is formed in the circuit. At this time, the resistor acts as a negative feedback in the circuit.
  1. Oscillation: Resistors and capacitors form an RC circuit, which can be connected in parallel and in series.
  1. Damping effect: Parallel resistors in the LC resonant circuit can reduce the Q value, and the resistors play a damping role at this time.
  1. Decoupling: The use of resistors in multi-stage amplifier circuits can prevent harmful low-frequency interference and thus play a decoupling effect.
  1. Convert electrical energy into internal energy (heating): When current passes through the resistor, it converts all (or part) of the electrical energy into internal energy, thereby generating heat. This principle is often used in electric furnaces and heaters in our lives.
  1. Convert current to voltage: When current flows through the resistor, a voltage will be generated across the resistor.

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