# Basic concepts

## Power in AC Circuit

Power in AC Circuit The instantaneous power of an AC waveform is given by p(t) = v(t) · i(t) Power in a Resistance The current and voltage are in phase on the resistor (Fig. 1). For a sinusoidal voltage, the instantaneous power is Here V and I are the RMS values of the voltage and …

## Personnel Protective Devices

Generally, it can be stated that a circuit breaker is intended to protect the electrical conductors in the circuit from overheating. It can also be stated that the equipment grounding conductor (EGC) is required by the NEC to be connected so that a low impedance fault current path is provided for the main purpose of …

## MCCB Circuit Breakers

Molded Case Circuit Breakers or MCCB circuit breakers are black plastic–cased automatic switches. They are designed to primarily protect insulating materials from overheating. Molded case circuit breakers (MCCB) are by far the most commonly used breakers in residential, commercial, and industrial facilities. When an MCCB has opened (or “tripped”) to protect the circuit, it can …

## What is power factor?

The term “power factor” (PF) is an expression of the relationship between the peak voltage and the peak current. Stated differently, the power factor is an expression of how far out of phase the voltage and current are to each other.  What is power factor? Figure 1 shows both voltage and current peaks occurring at …

## Fuse Selection Criteria

The fuse provides protection by melting away a thin metal link in the faulted circuit. The metal link may be of silver, copper, or nickel, silver being more common for long-term performance stability. The fuse body is generally filled with a sand-type filler (Figure 1) to suppress sparks when the fuse link melts and interrupts the …

## Thevenin Theorem Examples

Thevenin’s theorem is very useful in solving electrical networks which may not be easily solved by other methods. In this article, I will discuss this theorem and show some of the thevenin theorem examples to make this theorem easily understandable. Thévenin’s theorem is a circuit analysis technique that reduces any linear bilateral network to an equivalent …

## Kirchhoff’s Current Law Examples

The Kirchhoff’s Laws are very useful in solving electrical networks which may not be easily solved by Ohm’s Law. In this article, I will describe the Kirchhoff’s current law and will show some kirchhoff’s current law examples to make this law easily understandable. Kirchhoff’s current law states the following: The summation of currents entering a node …

## Superposition Theorem Examples

The superposition theorem is a method that allows us to determine the current through or the voltage across any resistor or branch in a network. The advantage of using this approach instead of mesh analysis or nodal analysis is that it is not necessary to use determinants or matrix algebra to analyze a given circuit. …

## Wheatstone Bridge Working Principle

Wheatstone Bridge Working Principle   Wheatstone devised a bridge-arrangement of resistances by which the resistance of a given conductor can be determined. This arrangement is called the ‘Wheatstone bridge‘.   In the arrangement, four resistances are so connected as to form a parallelogram. In one diagonal of this parallelogram is connected a galvanometer and in …

## Dia Para Ferro Magnetic Materials

Dia Para Ferro Magnetic Materials Diamagnetic Materials   These materials are feebly repelled by a magnet. When placed in a magnetizing field, they are feebly magnetized in a direction opposite to that of the field. Thus, the susceptibility of diamagnetic material is small and negative.   Further, the flux density in a diamagnetic material placed …