**Permeability**

Permeability is the measure of the ease, with which magnetic lines of force pass through a given material.

**Proton**

A positively charged particle with considerable mass.

**Phase rotation meter**

Phase rotation meter is a device used to determine the phase order of a three-phase electrical system.

## Parallel Circuit

In parallel circuits, the voltage drop V across each component remains same. However, the current through each element is different.

**Power Factor**

Power factor is described as the ratio between active power and apparent power. Mathematically, it can be described as:

**Power**

Power is the rate of doing work or the work per unit time. The unit of power is joule per second or watt.

**Period**

The time duration of one complete cycle.

**PERMANENT MAGNET**

Certain materials retain much of their magnetism long after an initial magnetizing force has been removed. These materials or bodies are called permanent magnet.

**POTENTIOMETER**

A potentiometer or a rheostat is an instrument used to measure and compare potentials without drawing any current from the circuit.

**Printed Circuit Boards**

Printed Circuit Boards are made of cooper-clad, epoxy-based material that has the wiring pattern etched on it to interconnect the various components.

**Phasor**

Phasor is a complex quantity which expresses phase and amplitude of a sinusoid.

**Peak Value**

The amplitude of a wave from the zero or reference axis to the maximum point in either direction.

**Pick-up**

The action of a relay as it makes designated responses to a progressive increase of input.

**Pickup value**

The minimum input that will cause a device to complete contact operation or similar designated action.

**Positive-sequence impedance**

The quotient of that component of positive-sequence sinusoidal voltage that is due to the positive-sequence component of current, divided by the positive-sequence component of the current at the same frequency.

**Positive-sequence network**

The equivalent representation of a power system constructed by using only the positive-sequence impedances of the various components.

**Power angle**

The phase angle between the generated voltage phasor and the terminal voltage phasor.

**Power-angle characteristic**

The expression for the real power developed by a synchronous machine in terms of its generated voltage, terminal voltage, synchronous reactance, and power angle.

**Power-angle curve**

The plot of the power-angle characteristic of a synchronous machine.

**Power factor**

The ratio of the average power in watts to the root-mean-square (RMS) volt-amperes.

**Power factor angle**

The angle whose cosine is the power factor.

**Power ﬂow equations**

The system of nonlinear algebraic equations relating the phasor bus voltages to the complex power Injections into the buses of the power system.

**Protective relay**

A device whose function is to detect defective lines or apparatus or other power system conditions of an abnormal or dangerous nature and to initiate an appropriate control action.

**Pull-out torque**

The maximum sustained torque that the synchronous machine will develop at synchronous speed with rated voltage applied at rated frequency and with normal excitation.

**Pilot Device**

Some type of audio-visual indicator or a type of switching device used to control the flow of energy to a process

**PLC scan**

The process the CPU goes through in order to execute a program.