Different types of Energy Meters

There are basically three types of energy meters: Electromechanical Energy Meter: The electromechanical induction meter operates by counting the revolutions of a non-magnetic, but electrically conductive, metal disc which is made to rotate at a speed proportional to the power passing through the meter. The number of revolutions is thus proportional to the energy usage. … Read more

Resistance of Semiconductors and Conductors as a Function of Temperature

In conductors i.e. metals the electrons that conduct current are called Itinerant electrons. They are essentially free to move around the metal, not bound to any particular atomic core. Resistivity can be understood as Itinerant electrons scattering off of Phonons, or thermal lattice vibrations, in a conductor. As the temperature of the metal increases, the … Read more

Difference between Current Transformer & Potential Transformer

Current Transformer (CT) and Potential Transformer (PT) are instrument transformers basically used for measurement and protection purpose in power systems. A Current Transformer (CT) is used to obtain reduced current signals for purpose of measurement, control and protection. They reduce the higher current to lower values which are suitable for operation of Relays and other … Read more

Capacitor – Conduction Current or Displacement Current

In a capacitor, we always have a Displacement Current and never a Conduction Current under normal conditions i.e. when we apply a potential difference across a Capacitor which is below its specified maximum Voltage. Conduction Currents flow when electrons actually move. But in Displacement Current, no charge carriers are involved. It’s just the variations in … Read more

Two Wattmeter Method – Measurement of Three Phase Power

There are three methods which are used for the measurement of three phase power in three phase circuits. The three methods are: Three Wattmeter Method Two Wattmeter Method Single Wattmeter Method In this post, we will discuss the Two Wattmeter Method for power measurement. Two Wattmeter Method: In two wattmeter method, a three phase balanced … Read more

Insulation Resistance Test and Polarization Index

Megger is an electrical device which is used to measure the Insulation Resistance by performing Insulation Resistance Test (IR Test). Basically Megger injects High DC Voltage across the Insulator and ground due to which leakage current flows through the Insulator to the ground. By measuring this Leakage Current, Megger calculates the Insulation Resistance. Suppose the … Read more

Measurement of Medium Resistance by Substitution Method

In Substitution Method, the Resistance whose value is to be measured is compared with the Standard Resistance by some technique which is described in this section. The connection diagram for Substitution Method is given below. Here, R is the unknown Resistance, S the Standard variable Resistance, A is Ammeter and r is Regulating Resistance. When … Read more

Voltmeter Ammeter Method for Measurement of Resistance

Resistance is classified into three categories for the sake of Measurement. Different categories of Resistance are measured by different technique. That’s why they are classified. They are classified as Low Resistance:  Resistance having value 1Ω or below are kept under this category. Medium Resistance: This category includes Resistance from 1Ω to 0.1 MΩ. High Resistance: … Read more


It is impossible to make a perfect / ideal circuit component which can have only one property. For example a Resistor do not have only resistance rather it have associated inductance and Capacitance too. Same is the case with Capacitor and Inductor. Therefore a circuit component have some impurity which causes unwanted quantities in the circuit known … Read more

Schering Bridge – Measurement of Capacitance and Dissipation Factor

We will discuss how to measure Capacitance and Dissipation Factor. Capacitance is measured by using Schering Bridge. What is this Schering Bridge? First we will discuss how to balance a bridge.   As we know for balanced bridge, there should not be any current through the detector which means the potential difference across the detector … Read more