A passive two-terminal semiconductor device that is used to protect electronic and electrical circuits is called Varistor. It protects against over-voltage by clamping of voltage. It is also known as a voltage dependant resistor (VDR) or non-linear resistor. The resistance of the varistor is changed due to the change in voltage across it. The varistors are non-ohmic variable resistors with symmetrical current and voltage features applicable for both DC and AC applications. In AC operations, … [Read more...]
What is a Rheostat : Working & Its Applications
In an electric circuit many times it is desirable to restrict the current, which can either be done by reducing the voltage or increasing the resistance in the circuit (Ohm’s Law). A rheostat is a device that facilitates this. The word rheostat is derived from the Greek language meaning changing stream (current). It is a must for any electrical laboratory/workshop in order to carry out experiments under variable current and voltage conditions. This is done by inserting a variable resistance in … [Read more...]
What is Megger : Construction, Working and Its Applications
It is quite easy to measure the resistance of a resistor. However, measuring the resistance of an insulator can be a difficult task. This is because the resistance of insulators is extremely high. For that, a device called megger is used which can be used to measure the relatively high value of resistance of insulators. The resistance is measured by comparing the unknown resistance of the insulator to that of the known value of resistance of a material. The circuit comprises two voltage coils … [Read more...]
What is Varistor : Working Principle, Construction and Its Applications
A resistor is an electric component that is used to limit the flow of current in an electric circuit. It is basically a resistive component. It has two terminals and is used in almost all electric circuits. It can also be sued to adjust signal levels and terminate transmission lines. There are different types of resistors available each meant for a specific purpose. A varistor is one such type of resistor, used to change the resistance in the circuit by changing the voltage. Its design is almost … [Read more...]
What is Thermistor : Working, Types & Applications
Temperature sensing is considered to be the most important part of any electronic application. In the household appliances or the industrial environment, the measurement of temperature to set certain limits for operation is needed. There are various sensors for this purpose some of them which are frequently preferred are Thermocouples, Semiconductor sensors, Resistance Temperature Detectors are popularly known as RTD's and Thermistor. While experimenting with the behavior of the … [Read more...]
What is Bleeder Resistor : Circuit Diagram and Its Functions
A resistor is used to restrict the flow of electric current in a circuit. It can also be used to reduce the voltage level in the circuit. A resistor has a huge variety of uses. It is a major component of any electric circuit. It is a passive component. Resistors may have either fixed or variable resistance. A bleeder resistor is basically a type of resistor which is connected across a capacitor in a circuit. It is basically used to drain out the excess charge from the capacitor. It is mainly … [Read more...]