Alternating Current and Voltage
Alternating current changes direction at regular intervals.
- Increased in value at a definite rate from zero to a maximum positive strength - Decreases back to zero - Then it flows in the opposite direction, similarly increasing to a maximum negative value, and again decreasing to zero.
The mathematical relationship between frequency and period is given as
1 Period is t=f 1 Frequency is f=t
There are some differences between DC and AC circuits.
1. Direct current flows constantly in only one direction with a constant polarity. 2. It changes magnitude only when the circuit is opened or closed, 1. Alternating current changes direction at regular intervals. 2. Then it flows in the opposite direction, similarly increasing to a maximum negative value, and again decreasing to zero.
Alternation current has largely replaced direct current in commercial power systems for a number of reasons.
1.) It can be transmitted over long distances 2.) More readily, more economically than direct current 3.) AC voltages can be increased or decreased by means of transformers.
Finally, most airplanes using a _______volt DC system have special equipment that requires a certain amount of ______cycle AC
24 volt 400 cycle AC
Generators used to produce an alternation current are called
AC generators or alternators
"AC" stands for _________________.
Alternation Current
In most AC motors no ___________ are required, and commutation trouble at high altitude is eliminated.
Brushes
The three regions in a transistor are the _____________, which is moderately doped, the ____________, which is heavily doped and the ____________ significantly less in its doping.
Collector (C) Emitter (E) Base (B)
_____________ the state of being continuous, uninterrupted or connected together.
Continuity
Electrical charge, which is symbolized by the letter Q, is measured in units of _____________.
Coulombs.
_______________ are used in AC power supply systems.
Current transformers
_________________ used in instrument circuits
Current transformers
A ____________ is a repetition of a pattern
Cycle
Whenever a voltage or current passes through a series of changes, returns to the starting point, and then again starts the same series of changes, the series is called a ____________.
Cycle
In its most basic form the capacitor is constructed of two parallel plates separated by a nonconductor, called a
Dielectric.
The capacitance of parallel plates is _______________ to their area.
Directly proportional
______________ the opposite of continuity, indication that a circuit is broken or not continuous.
Discontinuity
____________ is the process by which small amounts of additives called ______________ are added to the semiconductor material to increases their current flow by adding a few electrons or few holes.
Doping and Impurities
The ______________ is the most common type of primary cell battery and is similar in its characteristics to that of an electrolytic cell.
Dry cell
The _____________ value is also known as the RMS value or root mean square, which refers to the mathematical process by which the value is derived.
Effective
The term ____________ indicates that the output is a continuous sequence of pulses rather than having gaps that appear in the half wave rectifier.
Full wave
Diodes are primarily used for rectifier. This type of a rectifier is called a ____________ rectifier.
Full wave rectifiers
While ____________ is represented in a circuit by a coil, _______________ is represented by a capacitor.
Inductance Capacitance
Since alternating current constantly changes direction and intensity, the following two effects take place in AC circuits that do not occur in DC circuits:
Inductive reactance Capacitive reactance
An ___________________ value of voltage or current is the induced voltage or current flowing at any instant during a cycle.
Instantaneous
There are three values of alternation current, which are ________________ and _______________ and _____________.
Instantaneous Peak Effective
An ___________ is used in some aircraft systems to convert a portion of the aircraft's DC power to AC.
Inverter
The most common type of diodes are:
Light Emitting (LED) Liquid Crystal Displays (LCD) Photodiode Varactors
Fixed Capacitors
Mica Capacitors Ceramic Electrolytic
The transistors are classified as either ______ or ______ according to the arrangement of their N and P materials.
NPN or PNP
The _______________ in used to measure the resistance.
Ohmmeter
_____________ a circuit that is not a complete or continuous path.
Open circuit
When two waveforms go through their maximum and minimum points at different times, a phase difference will exist between the two.
Out of phase condition
The _____________ value is the largest instantaneous value.
Peak
In addition to frequency and cycle characteristics, alternating voltage and current also have a relationship called ________________.
Phase
_____________ is usually used in applications that require high current, such as power supplies
Power rectifier diodes
Types of Diodes
Power rectifier diodes Zener Diodes Special purpose diodes Light Emitting (LED) Liquid Crystal Displays (LCD) Photodiode
A transformer consist of three basic part
Primary winding Secondary winding Iron core
A ___________ is a device that transforms alternation current into direct current by limiting or regulation the direction of current flow.
Rectifier
Important property in AC circuits are _____________ and ______________ and _______________.
Resistance Inductance Capacitance
The are two basic types of inverters:
Rotary Static
The lead-acid car battery is a ____________.
Secondary cell battery
____________ an unintentional low resistance path between two components in a circuit or between a component or conductor and ground.
Short circuit
____________ and _____________ can be saved, since AC devices, especially motors, and smaller and simpler than DC devices.
Space and weight
There are two alternations in a complete cycle: ____________ and ______________.
The positive alternation and the negative Each is half a cycle.
Kirchhoff's current law,
The sum of all of the charging current is then equal to the total current.
A ____________ changes electrical energy of a given voltage into electrical energy at a different voltage level.
Transformer
AC voltages can be increased or decreased by means of _______________.
Transformers
The ___________ is a three terminal device primarily used to amplify signals and control current within a circuit
Transistors
Many of the principles, characteristics, and effects of AC are similar to those of direct current.
True
_____________ is simply a variable capacitance diode
Varactors
_______________ used for stepping up or stepping down voltage.
Voltage transformers
Two classes of transformers:
Voltage transformers Current transformers
The distance that a waveform travels during a period is commonly referred to as a _____________ and is indicated by the Greek letter lambda (A)
Wavelength
Two kinds of electrolytic capacitors are in use, ______________ and _____________.
Wet electrolytic Dry electrolytic
____________ (sometimes called ____________ diodes) are designed so that they will break down (allow current to pass) when the circuit potential is equal to or in excess of the desired reverse bias voltage.
Zener diodes Breakdown diodes
The basic unit of capacitance is the __________ and is given by the letter f.
farad
The standard unit of frequency measurement is the _________.
hertz (Hz).
The period of a sine wave is ______________ to the frequency. That is to say that the higher the frequency, the _____________________ will be.
inversely proportional shorter there period
The time required for a sine wave to complete one full cycle is called a _______________.
period
The frequency is __________________________ .
the number of cycles of alternation current per second (1 second)
When capacitors are connected in parallel, the effective plate area increases, and
the total capacitance is the sum of the individual capacitances.
