The resistances that range from about 1Ω to about 100 kΩ are classified as medium resistances. The resistances of most of electrical apparatus are the examples of medium resistances.Measurement of Medium ResistancesTo measure the medium resistances following methods are used −Ammeter-Voltmeter MethodSubstitution MethodWheatstone BridgeCarey-Foster Slide-Wire Bridge Method.Ammeter-Voltmeter MethodIn this method, current ... Read More

The resistances of the values of less than or equal to 1 Ω are classified as low resistances. For example, the resistances of armatures and series windings of large machines, ammeter shunts, contacts, etc.Measurement of Low ResistancesFor the measurement of low resistances, the following methods are used −Ammeter-Voltmeter MethodPotentiometer MethodKelvin Double ... Read More

Resistances of the order of 100 kΩ and upwards are classified as high resistances. For example, insulation resistances.Measurement of High ResistancesThe following methods are employed for the measurement of high resistances −Direct Deflection MethodLoss of Charge MethodMegohm BridgeMeggerDirect Deflection MethodIn this method, a very sensitive and high resistance (more than ... Read More

Resistance in an AC CircuitConsider the circuit diagram, containing an AC sinusoidal voltage source and an unknown passive element (K). The element K will be a resistance, only if the voltage across it and the current flowing through it, are in phase with each other.ExplanationLet the equation for alternating voltage ... Read More

One of the remarkable discoveries in the field of electrical engineering is the grounding of electric current. In an electric circuit, there be an active wire, which supplies current and a neutral wire, which carries that current back. An additional grounding wire can be attached to outlets and other electrical ... Read More

Power in AC circuitActive Power (P)The product of voltage (RMS) and current (RMS) with the cosine of the angle between them, in an AC circuit is termed as active power. It is measured in watts (W). For a pure inductive and pure capacitive circuit, the active power being zero.Active Power, ... Read More

The power transformers are design to operate with an almost constant load which is equal to their rating. The maximum efficiency being designed to be at full load. Therefore, the fullload winding copper losses must be equal to the core losses.Actually, all the transformers are the same that is same ... Read More

An oscilloscope is a device which allows the amplitude of electrical signals (current, voltage, power etc.) to be display as a function of time.Oscilloscope Parts and their FunctionAn oscilloscope consists of following major parts (see the block diagram) −Cathode Ray Tube (CRT) – The CRT displays the quantity being measured. ... Read More

A device that can measure the resistance directly is known as an ohmmeter. There are two types of ohmmeters asSeries Types OhmmeterShunt Type OhmmeterSeries Type OhmmeterCircuit DiagramThe circuit of a series type ohmmeter consists of a D’Arsonval galvanometer (PMMC meter) connected in series with a resistance and a battery. It ... Read More

When the two coils are arranged in such a way that a change of current in one coil causes an emf to be induced in the other, the coils are said to have mutual inductance. The mutual inductance is denoted letter M and measured in Henry.Consider two coils, coil 1 ... Read More