# A

## Average Value

The sum of the instantaneous voltages in a half cycle wave shape divided by the number of instantaneous voltages. In a sine wave, it is equal to 0.637 times the peak voltage.

## Analog meters

Analog meters are a multifunctional multimeter that operates based on electrical mechanical movement.

## Autotransformer

A transformer with a single electric winding, which can be used as a step-down or step-up device; a transformer characterized by no electrical isolation between primary and secondary.

The reciprocal of a circuit’s impedance, measured in Siemens.

## Atom

The atom is made up of subatomic particles, the most important of which are the electrons and protons.

## Ammeter

An Ammeter is a device used for the measurement of current in amperes (or even in smaller units like mA or μA).

## American Wire Gauge (AWG)

The system of notation for measuring the size of conductors or wires.

## Alternating Current

An electric current that periodically changes its direction, usually many times per second.

## Air-Gap Power

It is the power transferred from the machine stator to the rotor across the air gap.

## Aluminum conductor steel reinforced (ACSR)

ACSR is a composite conductor which is made up of an amalgamation of aluminum wires surrounding the steel.

## Ampere’s law

The magnetic ﬁeld strength, at any point in the neighborhood of a circuit in which there is a current i, is equal to the vector sum of the contributions from all the differential elements of the circuit. The contribution dH, caused by a current i in an element ds at a distance r from a point P is given by

$d\text{H}=\frac{r[\text{r}*\text{ds}]}{{{r}^{2}}}$

## An-bn-cn or abc sequence

The order in which the successive members of the set reach their positive maximum values. Phase a is followed by phase b and then by phase c.

## Apparent power

The product of the root-mean-square voltage and the root-mean-square current.

## Armature Winding

The winding in which AC voltage is produced by relative motion with respect to a magnetic field.

## Average power

The time average of the instantaneous power; the average being taken over one period.

## Analog Signal

A signal with a varying voltage or current.  A continuous set of values.

## Auto Ranging

A term used to describe test equipment where the test equipment automatically adjusts the range to display the correct readout. For example, if you are measuring a voltage under 2 volts, you would select read voltage and the meter would automatically read the voltage and display the value.