ASVAB: Electronics Information

PNP Transistor

2 pieces of p-type material that had a piece of n-type material between them

capacitors

(condenses), electrical storage units. Constructed using 2 metal conduction plates with a thin insulator (dielectric) between them. Air can sere as a dielectric)

counter-electromotive force

(counter-wmf), the expanding magnetic field generates a voltage in the coil that opposes the original flow. The current is cut off, the magnetic field then collapses, and this collapsing magnetic field generates a voltage in the could that keeps the current flowing

electrical potential difference

(electromotive force) known as voltage

electrical potential

(pressure like quality) electrons will tend to be pushed from areas of greater ____________, areas of lesser electrical pressure (lower pressure)

capacitive reactance

A capacitor's opposition to the flow of current, measured in ohms. ________ is inversely proportions to the frequency of the AC signal. The higher the frequency, the less opposition there is to the flow of AC across the capacitor

transformers

A device that increases or decreases the voltage of alternating current; alternating current flowing in wires wrapped around an iron core magnetizes the core, and produces a changing magnetic field in the core. Changing magnetic fields generates a voltage in a neighboring coil of wire.

alternating current (AC)

A flow of electric charge that regularly reverses its direction many times in a second as it moves in a conductor. Household electrical outlets deliver __________. Provides a more efficient way to transport electricity from the power stations to your homes or businesses

potentiometer

A switch that can provide variable motion control. It can vary the resistance within the switch, which affects both the current and voltage flowing out of the switch. Example: electronic applications can be used to help adjust the volume on a TV, radio, or stereo

solid-state device

An electronic device with no moving parts. A storage device that uses memory chips instead of spinning disks (such as those used by magnetic hard drives and CD drives.) Example of solid state devices are jump drives, flash memory cards, and solid state disks used as hard drives in notebook computers designed for the most rugged users. Also called solid state drive or solid state disk

conventional current

Current that flows from the positive side of the battery to the negative side. This is the way current is drawn in circuit diagrams, even though it is wrong.protons stay in the nucleus and don't move, if a circuit has a conventional current that is moving in a clockwise directions. Electrons are moving around the circuit in a counter-clockwise direction. ______________ or election flow of electrons, remember to switch the direction when going from 1 to the other

resistors

Devices that apply resistance to a circuit to manage current or voltage; it creates a specific amount of resistance that generates a voltage drop when current passes through it. An increase in R will cause a decrease in the current

2 types of current

Direct current and alternating current

current flow in a NPN transistor

PNP transistors work opposite to NPN transistors. A PNP transistor requires a (-) voltage at the base to turn it on, and the current then flows from the emitter to the collector

doping

Process of adding impurities to a semiconductor to increase its conductivity

rectification

The process by which alternating current is changed to pulsating direct current

parallel circuits

Two or more paths that electricity can flow through, and there is a load connected to each path. Current flow becomes divided when there are parallel paths. Electricity follows eery possible path, though a larger portion of electrons will take a path of low resistance which a smaller proportion will take a path with higher resistance. The total current through the circuit is = to the sum of currents through each closed path

series-parallel circuit

a circuit that has many components, such as an on/off switch, wired in series with a number of loads that are connected in parallel. Most residential wiring; wall outlets are wired in parallel, are all fed from a circuit breakers that is wired in a series. Switching off the circuit breaker will turnoff power to all of the outlets. If the circuit breaker is on, voltage provided to all of the outlets where they are plugged or not

short circuit

a connection that allows current to take the path of least resistance; current and resistance are inversely proportional. Flow of current will increase. Caused by insulation on the wires leading to and from the load becoming frayed and allowing the wires to come into direct contact with each other. ___________ occurs in part of a series circuit, the net effect is merely to remove the load that was bypassed as a result of the _________. Occurs at any load in parallel circuits or bypasses all the loads in series circuits, the resistance of the circuit asa whole is reduced to near zero and a dangerous surge in current

ammeter

a device that measures current

reverse-biased

a diode connected in a circuit such that the p-type terminal is more negative than the n-type terminal

forward-biased

a diode connected in a circuit such that the p-type terminal is more positive than the n-type terminal; current is able to flow

variable resistor

a resistor whose resistance can be changed (rheostats or potentiometer)

transistor

a small electronic device used in a circuit as an amplifier or switch

load

a source of resistance that converts electrical energy into some other energy form. Examples: a light bulb, has resistance and converts electrical energy into light energy and heat. Electric motors, heating elements, and solenoids. If a load resistance were to decrease, the current flowing in the circuit would increase. Is any component with resistance that converts electrical energy into some other energy form. If the circuit were broken, as in wire (conductor) being disconnected, no current will flow

tools to measure resistance

ammeter and voltmeter

series circuit

an electrical circuit that has only 1 path for current to flow. A break (opening) at any point in the circuit will cause current to stop flowing in all parts of the circuit. Simplest possible circuit, 1 voltage source connected to 1 load by conductors. Only 1 path for current to follow, current will be the same in all parts of the circuit

coils

depending on the number of turns of the wire is primary versus the secondary coil, the proximity of the coils, a smaller or larger voltage can be induced in the secondary coil. Primary coil is the 1 that s connected to the source. Secondary coil is the 1 in which an electric current is induced. Larger number of secondary coils means larger voltage. Closer the secondary coils are to the primary coils, the more efficient the transformer is in producing a voltage in the secondary coils

ohmmeter

device that measures resistance

direct current (DC)

electric current that flows in only one direction in a conductor; this type of current is delivered by a battery. Many electronic devices, cell phones, and laptops use DC

charge

electrical current is measured by the amount of charge, flowing past per unit of time

grounding

electrical devices and residential wiring is an important safety factor

voltage

electrical pressure, is measured in volts (symbolized by the letter V)

shells

electrons occupy various energy levels around the nucleus; each time one becomes fully new one is begun

reactants

elements or compounds that enter into a chemical reaction

semiconductors

elements that have 4 electrons in its valence shell. The bond between these 4 electrons and the nucleus are somewhat strong, elements are neither good conductors nor good insulators. Examples: silicon and germanium

important safety components in a circuit

fuses and circuit breakers

aluminium

has a higher resistance than copper, exhibits some other characteristics make it even less Tham desirable fir use in electrical applications

insulator

has a valence shell more than half full, or completely full. It does not conduct electricity much at all, because its electrons are all tightly bound, and will not lead their packed valence shells

copper

has only a slightly higher resistance than silver, much less expensive. Most electrical cable wire is now used out of this element

coulomb (C)

how ampere is defined, basic unit of electrical charge, flowing past a given point in 1 second. symbol for amperes is A. Example: If 5 coulomb if charge were to pass by a point per second, this would be a current of 5 amps (5A). 1 coulomb, is the amount of negative charge in 6.25X10^18 electrons

amperes

how current is measured (amps for short)

ohm

how resistance is measured; 1ohm is defined as the amount of resistance that will allow 1 ampere of current to flow if 1 volt of electrical pressure is placed on a conductor

directly proportional

how voltage and current relate

what happens if multiple loads were found in a series circuit?

if 2 or more loads are added to a series circuit, their resistances add together, creating whats called the total or effective resistance across the circuit. Voltage, (electrical pressure)at 2 different point (from the (-) to the (+) terminals of a voltage source), can also be calculated across a single load. Known as voltage across a load, and the total drops across each load in a series circuit is = to the voltage source itself

open circuit

if the circuit's broken, as in a wire (conductor) being disconnected, no current will flow. When current is flowing, each electron is carrying the voltage the length of the conductor: pushing the electrons ahead of them to keep moving forward, being pushed themselves by those behind. When the line stops, it stops everywhere, when there is no clear path toothier destination. In the gap that occurs in an open circuit, electron flow entirely and the current is zero

electrons

in motion around the nucleus and have a (-) charge. For a neutral atom, there is 1 electron for each proton that resides int he nucleus

circuit

is a complete looper path that electricity can flow. 3 essential components of an electrical circuit: a voltage source, a load, and conductors to connect the load to the voltage source

chemical reaction

the process by which one or more substances change to produce one or more different substances; atoms are rearranged into new combinations, resulting n different kinds of molecules

conductor

is an element that allows electrons to flow freely. 1 or more mobile valence electrons per atom that are free to move from 1 atom to another, as each valence shell has more empty spots than electrons. Is just a wire that connects the load(s) and voltage source. he wire is often considered to have zero resistance. This is not true, resistance in a conducting wire is often small enough compared to any given load that it can, be ignored for most calculations. At zero resistance, Ohm's law requires the voltage across such a conducting wire to also be zero, meaning the electrical pressure does not change from 1 side to another

NPN Transistor

made up of a thin piece of p-type material sandwiched between 2 pieces of n-type material

simple series circuit with unknown resistance, how could you go about determining the value of resistance in the circuit?

measure resistance directly using an ohmmeter. Remove the device with unknown resistance from the circuit or disconnect the power source from the circuit (ohmmeter has own power source). Measured by attaching the ohmmeter leads across both ends of the device. If not available, ohmmeter connected in series with he resistor and a voltmeter connected parallel with the resistor

voltmeter

measures voltage

cathode

negative electrode; n-type material connected to the batteries (-) terminal

capacitor symbol

only allows AC to flow

resistance

opposite of the flow of current

rheostats

or foot controls used to operate the hand pieces; useful in changing the current in a circuit. Example: used at light dimmers or to control the speed of small motorized devices

valence shells

outer shell of an atom, number of electrons that reside in the ______________ are what determines whether an element is a conductor, semiconductor, or insulator

anode

positive electrode; p-type material connected to the batteries (+) terminal

magnetic fields

produced by moving charges, the moving electrons in a circuit are no exception. Current-carrying wire generates its own _____________. Strength of the field depends on the amount of current flowing in the wires. The wires are wrapped around a ferrous material and a current is passed through the wires, the resulting ___________ magnetizes the iron core, producing an electromagnet. Magnetism is the basic principle behind many of the aforementioned electrical devices

ground

represents a place of lowest potential n a circuit. Potential difference (voltage) is largest between any point in the circuit and the _________ point, any "stray" electricity will follow this path since resistance is low here. This prevents shock due to external influences such as lightening, or due to internal circuit failure where conducting wires are compromised

inductors

resistance to the change in current flow in a circuit is known as self induction and is a property exhibited by electrical components. Inductors resist change in current flow. If current is increasing, inductor opposes the increase by generating a voltage that moves against the applied current. Current decreases, the inductor uses the magnetic energy in the coil opposes the decrease and to keep the current flowing

fixed Resistor

resistors that have a value that cannot be changed; use a color band system to enable us to determine their resistance in ohms. First colors gives the 1st number. 2nd color gives the second number, 3rd number gives multiplier or the number of 0s behind the numbers

n-type material

semiconductor with extra electrons, creates negative charge. Free electrons move from negative areas to positive areas Cathode

p-type material

semiconductor with extra holes, has extra positively charged atoms, electrons just from hole to hole, moving from negatively charged areas to positive Anode

atoms

smallest particles that elements can be broken into and still retain the properties of that element. An atom is itself broken into even smaller components, called subatomic particles. 2 subatomic particles are found within the nucleus: protons and neutrons. Nucleus is the heaviest part of an atom

simple condensor

store an electrical charge because the DC source creates an excess of electrons on the (-) plate and a shortage of electrons on the (+) plate. Electrostatic attraction between the (+) and (-) charges keep the charge intact in the capacitor, men when the voltage is removed. Will discharge itself if a conductor is connected across it, as a path is then created for electrons to flow from the (-) plate to the (+) plate. Capacitor will allowAC to flow across it, but will block DC. Why DC is most useful for "charging up" a capacitor

magnetic field formed by a current carrying wire can be made __________

stronger by winding the wire into a coil. The coil is wound onto a ferrous (iron) core, magnetic field around the coil becomes even stronger, since magnetic lines of force travel more easily through iron than through air. Current first flows through a coil, magnetic fields build relatively slowly

circuit breakers

switches that will bend away from circuits as they heat up; have the advantage of being able to be refused multiple times. Respond more slowly to increase in current that fuses do, more expensive to install. Several types of breakers. 1 class of circuit breaker consists of a bimetallic strip that bends away from its contact in a circuit when too much current is flowing. Makes a break in the circuit and prevents flow. Another, uses electromagnet to cause a breach. When the current flow rises to a certain value, the ferrous material is sufficiently magnetized to cause the circuit to open, inhibiting further current flow

capacitance

the ability of a capacitor to store charge, represented by the symbol C

silver

the best conductor, exhibits the lowest resistance. Relatively expensive

ohms law

the current in a circuit equals the voltage difference divided by the resistance; V=IR V=voltage, I=current, R=resistance. Voltage source is the beginning and end of the circuit

electrical power

the rate at which electrical energy is converted to another form of energy; electrons moving through a large voltage has more energy. High currency means more electrons passing by each moment. So an equivalent rate of energy delivery can be achieved by a smaller number of electrons each moment (lower current) with a larger amount of energy per electron (higher voltage), or a larger number of electrons each moment (higher current ) with a smaller amount of energy per electron (lower voltage)

current

the rate of flow of electrons through a conductor

inversely proportional

the relationship between two variables whose product is constant; current and resistance. The smaller the resistance a material has, the better a conductor it is. Anytime voltage increases, current will also increase. Materials with high resistance (poorer conductors), a higher voltage must be used to get the same current. All conductors have a certain amount of resistance, some more than others. 3 materials used as conductors: silver, copper, and aluminum

products

the substances that are formed by the chemical change. Example:water is also known as H2O because a single water molecule is made of 2 hydrogen atoms and oxygen atom. One kind of chemical reaction will cause many water molecules to break apart and the atoms to rearrange into hydrogen molecules (H2) and oxygen molecules (O2)

closed (complete) circuit

these 3 components are connected so that current can flow

fuses

thin wires that melt when current exceeds a prescribed amount, preventing any more electrical flow. Prevents any potential damage to the electrical device. Disadvantage is that when it has melted, or "blown", it has to be replaced before the circuit works again. ______ with current rating can be used depending on the device specifications

farad

unit of capacitance; a ______ is sufficient capacitance to store 1 coulomb of electrons with an electrical potential of 1 volt applied

henries

unit of inductance; the symbol used to repress induction is L. Inductors work opposite of capacitors, the sense that they allow DC to pass easily, resist the flow of AC. Resistance to current flow is knows as inductee reactance, measured in ohms. Increases with increasing frequency of the AC signal

semiconductor

valence shell that is exactly half full, is neither a good conductor nor a good insulator, but it has some remarkable properties that make it very useful for making electronic components

diodes

when P-type and N-type are joined. A component that lets current flow in one direction better than the other direction

inside a transistor

wires connect to the 3 pieces of semiconductor material. Each piece has a name: base-middle piece collector-outside piece emitter-outside piece The symbol for the transistor has an arrow that identifies which type the of emitter. Direction of the arrow tells us what type of transistor it is. The arrow always points in the direction of the n-type material