Fundamentals of Electricity Flashcards

Question

Hole

Answer 1

The movement of an electron from one atom to the next, creating the appearance of a positive charge moving in the opposite direction

Answer 2

Negative to Positive: electron flow and current flow Positive to Negative: hole flow

Answer 3

- Supplies electrons from one end of the conductor - Removes electrons from the other end of the conductor - Can be thought of as a kind of a pump

Answer 4

- Friction - Magnetism - Chemicals - Light - Heat - Pressure

Answer 5

Van de Graaff generator, lightning storm

Answer 6

- Most common method of producing electrical energy - Produced using a generator - Powered by steam from nuclear power or coal, water, wind or gasoline or diesel engines.

Answer 7

- Cell (1.5 V) - Second most popular method of producing electrical energy - Consists of two metals - Copper - Zinc - Many cells can be connected to form a battery

Answer 8

- Photovoltaic cell - A single cell can produce a small voltage - Many cells must be linked to produce a usable voltage and current - Primarily used in satellites and cameras - Cost is high but is declining

Answer 9

- Thermocouple - Two dissimilar wires twisted together - Voltage is directly proportional to the amount of heat applied - Used in thermometers - Also called a pyrometer

Answer 10

- Piezoelectric effect - Voltage is small; must be amplified to be useful - Used in crystal microphones, phonograph pickups (crystal cartridges) and precision oscillators

Answer 11

Electrons flow in only one direction

Answer 12

Electrons flow in one direction then in the opposite direction

Answer 13

A combination of two or more cells

Answer 14

- Cells that can not be recharged - Leclanche cell or dry cell; also referred to as a carbon-zinc cell - Alkaline cell - Lithium cell (last longer)

Answer 15

- Cells that can be recharged - Lead-acid battery or wet cell - Nickel- Cadmium cell or Ni-Cad

Answer 16

- Series - Series - It = I1 = I2 = I3 (current) - Vt = V1 + V2 + V3 - Series opposing - Little practical value - Parallel - It = I1 + I2 + I3 - Vt = V1 = V2 = V3

Answer 17

Voltage rise: Potential energy or voltage introduced into a circuit Voltage drop: The energy given up as electrons encounter resistance in the circuit

Answer 18

- Earth - Used to prevent electric shock. - Electrical - Provides a common reference point.

Answer 19

- Opposition to electron flow in a circuit - Expressed by the symbol R - Measured in ohms - Abbreviated with Greek symbol Ω - Varies from material to material - Silver is the best - Copper is the most common - Gold doesn't tarnish - Affected by temperature - Affected by the size diameter of the conductor

Answer 20

The resistance of a material to current flow - Resistivity is different for different materials - Even good conductors have different levels of resistivity Compare everything to silver

Answer 21

- The ability of a material to pass electrons - Expressed as G - Unit known as Mho (ohm backwards) - Abbreviated with the inverted Greek symbol ℧ - is derived by R = 1/G or G = 1/R

Answer 22

- Components manufactured to possess a specific value of resistance to the flow of current - Come in two classifications: - Fixed value - Variable - Variety of shapes and sizes to meet specific circuit, space and operating requirements

Answer 23

- The amount that the resistor may vary and still be acceptable - The larger the tolerance the cheaper it is to manufacture - Resistors are available with tolerances of +-20%, 10%, 5%, 2% and 1%

Answer 24

- The most commonly used - Inexpensive - Manufactured in standard resistor values

Answer 25

- Used in high-current circuits - Resistance varies from a fraction of an ohm to several thousand ohms

Answer 26

- Becoming increasingly popular - Three types : carbon film, metal film and tin oxide film

Answer 27

- Ideal for small circuit applications - Available in both thick and think films

Answer 28

- Allow the resistance to vary - Vary linearly or logarithmically - Called a potentiometer when used to control voltage - Called a rheostat when used to control current

Answer 29

- Alphanumeric - Example of an alphanumeric code - RN60D5112F RN60 = Resistor style (composition, wirewound, film) D = Characteristics (effects of temperature) 5112 = Resistance value (2 represents the number of zeros) F = Tolerance - EIA (Electronic Industries Association) Color code

Answer 30

- Resistors are typically configured in a circuit in one of three different ways - Series circuit configuration (voltage divider) - Parallel circuit configuration (current divider) - 1/Rt = 1/R1 + 1/R2 + ... + 1/Rn - 1/Rt is always less than the least Rn - Compound circuit configuration

Answer 31

- The path that the current follows is called an electric circuit - All electric circuits consist of - A voltage source - A load (convert energy to different form) - A conductor

Answer 32

In GR Kirchhoff extended Ohm's Law with two important statement Kirchhoff's current law The Algebraic sum of all the current entering and leaving a junction is equal to zero Kirchhoff's voltage law The Algebraic sum of all the voltages around a closed circuit equals zero

Answer 33

- Relates to the rate at which work is being done. - Work is done when a force (voltage) causes motion (current) - Voltage creates current, causing electrons to move in a circuit - The total power dissipated in a series or parallel circuit is equal to the sum of the power dissipated by the individual components

Answer 34

- The instantaneous rate at which work is done - Measured in watts - Wattage is greater when work is done in a short period of time than when the same amount of work is done in a longer period of time.

Answer 35

- The basic unit of power - Equal to the voltage across a circuit, multiplied by the current through the circuit - Represents the rate at which work is being done P = I * E The power dissipated in a circuit is often less than 1 watt

Answer 36

To determine the power dissipated by a component - Voltage drop times current

Answer 37

Used to set a bias or operating point of various active electronic components - Transistors - Integrated circuits Used to divide a higher voltage to a lower voltage Ofen referred to as scaling

Answer 38

Current is directly proportional to the voltage across the circuit The voltage drop is equal to the percentage of the dropping resistor to the sum of the dropping network E (drop) = E (source) * R (drop) / R (total)

Answer 39

The current flow into the first component in the circuit to start the voltage division process Should have 1/10 of the amp of the overall load current (rule of thumb)

Answer 40

- Natural magnet - Derived from magnetite - Artificial magnet - Created by ribbing a piece of soft iron with a piece of magnetite - Electromagnet - Created by current flowing through a coil of wire

Answer 41

The north magnetic pole is different from the north geographic pole

Answer 42

Red for the north pole Blue for the south pole

Answer 43

Can be traced to the atom As electrons orbit the nucleus, they also spin on their axis This electrostatic charge produces a magnetic field The direction of the magnetic field is the same as the electron's direction of spin

Answer 44

Materials that respond to magnetic fields, like our fridge. when it is ferrie, it would rust Atoms combine into domains or groups When unmagnetized, the domains are random When magnetized, the domains align in a common direction and the material becomes a magnet

Answer 45

The invisible lines of force surround a magnet. These are called flux lines Flex lines - Have polarity from North to South - Always form a complete loop - Do not cross each other - Tend to form the smallest possible loop

Answer 46

The ability of a material to accept magnetic lines of force If a magnets stick to it, it has a high level of permeability

Answer 47

A magnetic field is generated when current flows through a wire.

Answer 48

Composed of many turns of wire close together The principle of the electronmagnet - When a wire is twisted into a loop - The flux lines are brought together - The flux lines are concentrated at the center of the loop - A north and south pole are established The strength of the magnetic field can be increased three ways - The more turns of wire, the more flux lines are added together - The greater the current, the greater the number of flux lines generated - A ferromagnetic core is inserted into the center of the coil, usually iron

Answer 49

The effect a magnet has on an object without physical contact

Answer 50

The magnetic field that remains when an object is separated from a magnet.

Answer 51

The ability of a material to retain its magnetic field after the magnetizing force is removed

Answer 52

Low reluctance materials Used to protect electronic equipment from magnetic flux lines

Answer 53

The principle behind the generation of electricity - A current is produced when a conductor passed or is passed by a magnetic field - As the conductor passes through the magnetic field, a deficiency of electrons is created - This results in a difference of potential between the ends of the conductor - When the conductor is removed from the magnetic field, the free electrons return to their parent atoms.

Answer 54

The induced voltage in a conductor is directly proportional to the rate at which the conductor CUTS the magnetic lines of force.

Answer 55

Thumb Motion Index Flux (North to South) Middle Current (Negative to positive)

Answer 56

- AC generator: converts mechanical energy to electrical energy by utilizing the principle of electromagnetic induction. - DC generator: functions like an AC generator with the exception that it converts the AC voltage to DC voltage.

Answer 57

An electromagnetic switch that opens and closes with an electromagnetic coil - Used where it is desirable to have one circuit control another circuit - it electrically isolates the two circuits - Also used to control several circuits some distance away - Doorbell

Answer 58

A coil, when energized, pulls a plunger that does some mechanical work - Door chimes - Automotive starters

Answer 59

Used the electromagnetic principle - A magnetic field is produced by a permanent magnet attached to the stylus - The stylus tracks through the groove of a record in response to the audio signal recorded - The movement induces a small voltage that varies at the audio signal response - The induced voltage is amplified and used to drive a loudspeaker, rpoducing the audio signal

Answer 60

Constructed of a moving coil around a permanent magnet - The magnet produces a stationary magnetic field. - The current passes through the coil, producing a magnetic field that varies at the rate of the audio signal - The magnetic field of the coil is attracted and repelled by the field of the magnet - The coil is attached to a cone that moves in response to the audio signal - The cone reproduces the audio signal

Answer 61

Uses the electromagnetic principle to store information - A signal is stored on tape or disk with a record head, to be read back later with a playback head. -- Some are combined in one package -- They may be on the same head - The record and playback heads are a coil of wire with a ferromagnetic core. - A tiny gap between the ends of the core is a magnetic field - A piece of material covered with iron oxide, is pulled across the record head, magnetizing it. -- Information is written in a magnetized pattern - To play back or read the information, the material is moved past the gap in the playback head - The magnetic field induces a small voltage into the coil winding - When amplified, the information is reproduced. Examples - Floppy disk drives - Hard disk drives - Reel to reel recorders - Cassette recorders - Video recorder

Answer 62

Operation depends on the principle that a current-carrying conductor, placed in and at right angles to a magnetic field, tends to move at right angles to the direction of the field.

Answer 63

Uses the current-carrying principle - The conductor carrying current is deflected by a magnetic field - The electrons travel through a vacuum to strike a phosphor screen where they emit light - By varying the electron beam over the surface of the picture screen, a picture can be created. - Two magnetic fields deflect the beam -- One field moves the beam from side to side -- One field moves the beam up and down

Answer 64

The characteristic of an electrical conductor that opposes a change in current flow The symbol for inductance is L Once current is moving through a conductor. Inductance helps to keep it moving As the magnetic flux lines build up. They create opposition to the flow of current Is measured by the henry - Named after Joseph Henry - Represented by H - The amount of inductance required to induce an emf of 1 volt when the current in a conductor changes at the rate of 1 ampere per second - Most commonly used are the millihenry (mH) and the microhenry(uH)

Answer 65

A device that stores energy in a magnetic field Designed to have a specific inductance Consist of a conductor coiled around a core Classified by the type of core material, magnetic or nonmagnetic When calculate inductance, it works just like resistance in series and parallel

Answer 66

An induced emf in any circuit is always in a direction to oppose the effect that produced it. The amount of counter emf is in proportion to the rate of change. The faster the rate of change, the greater the counter emf

Answer 67

The time required for current through a conductor to increase to 63.2% or decrease to 36.8% of the maximum current Expressed as t = L / R t = time in seconds L= Inductance in henries R = Resistance in ohms 5 time constants required to fully build up or collapse the magnetic field of an inductor

Answer 68

- Air core - Fernte or pawdered Ion core - Toroid core - Shielded core - Laminated core

Answer 69

The ability of a device to store electrical energy in an electrostatic field The letter C stands for capacitance Similar to storage cells The basic unit of capacitance is the farad (F) A farad is the amount of capacitance that can store 1 coulomb (C) of charge when the capacitor is charged to 1 volt

Answer 70

A device that possesses a specific amount of capacitance Made of two conductors separated by an insulator - The conductors are called plates The insulators are called dielectric Treat all capacitors as though they were charged - Never touch both leads of a capacitor with your hands - A capacitor can hold a potential indefinitely if it does not have a discharge path Factors affecting capacitance - Area of the plate - Distance between the plates - Type of dielectric material - Temperature

Answer 71

A measure of the effectiveness of a material as an insulator Some examples Paper: 2~3 Meca: 5~6

Answer 72

Large capacitance for size and weight Consists of two metal foils separated by fine gauze saturated with a chemical paste called an electrolyte Polarized, having a positive and negative lead

Answer 73

The opposite as resistance in series and parallel

Answer 74

Reflects the time required for a capacitor to charge up to 63.2% of the applied voltage or to discharge down to 63.2% t =RC t = time in seconds R = resistance in ohms C = capacitance in farads

Answer 75

The father of AC is Nikola Tesla

Answer 76

Cycle: each time the AC generator completes on revolution, its output voltage is referred to as one cycle of output voltage. It produces one cycle of output current in a complete circuit The two halves of a cycle are called alternations Two complete alternations make up a cycle One cycle per second is called a hertz (Hz)

Answer 77

The rotating loop of wire

Answer 78

Each point on a sine wave has two numbers associated with it - The degree of rotation: the angle to which the armature has rotated - The amplitude: The maximum departure of the value of an alternating current or wave from the average value

Answer 79

The amount that produces the same degree of heat in a given resistance as an equal amount of direct current Can be determined by the root mean square (rms) process Also called the rms value Erms = 0.707E(peak)

Answer 80

The time required to complete one cycle of a sine wave Measure in seconds The letter t is used to represent period

Answer 81

The number of cycles that occur in a specific period of time Expressed in terms of cycles per second Unit of frequency is called hertz One hertz equals one cycle per second

Answer 82

Higher frequency sine waves that are exact multiples of the fundamental frequency (Represents the repetition rate of the waveform) Odd harmonics are odd multiples of the FF, Even ...

Answer 83

Moving coil meter movement - Referred to as D'Arsonval meter movement - Designed to measure DC current - AC current must be converted to DC current to be measured - The process is called rectification - The rectifiers covert the sine wave into a pulsating DC current

Answer 84

Most versatile piece of test equipment available for working on electronic equipment and circuits Provide a visual display of what is occurring in the circuit Oscilloscope provides - The frequency of a signal - The duration of a signal - The phase relationship between signal waveforms - The shape of a signal's waveform - The amplitude of a signal The basic parts of an oscilloscope are - A cathode ray tube (CRT) - A sweep generator - Horizontal and vertical deflection amplifiers - Power supplies

Answer 85

Just resistive load NO inductor and Capacitor

Answer 86

Capacitors in AC circuits - AC voltage applied to a capacitor, gives the appearance that electrons are flowing in the circuit - Current and voltage do not flow in phase with each other -- 90 degrees out of phase -- Current leads voltage

Answer 87

The opposition that capacitor offers to the applied AC voltage Represented by Xc Measured in ohms Calculated by using the formula Xc = 1 / 2π * fc f stands for frequency c stands capacitance Can be used alone or combined with resistors to form RC (resistor-capacitor) networks Used for filtering, phase shifting, coupling and decoupling

Answer 88

A circuit that discriminates among frequencies, attenuating (weakening) some while allowing others to pass Low pass filter and high pass filter

Answer 89

Inductors offer opposition to the current flow - Voltage placed across an inductor creates a magnetic field - When AC voltage changes polarity, it causes the magnetic field to expand and collapse. - Voltage is induced in the inductor coil called a counter-electromotive force (CEMF) -- 180 degrees out of phase with the applied voltage -- Opposes the applied voltage -- Opposition is as effective in reducing current flow as a resistor Voltage leading current, ELI, 90 degrees

Answer 90

The opposition offered to current flow by an inductor Measured in ohms Depends on its inductance and the frequency of the applied voltage Expressed by the symbol Xl Xl=2π * fl l = inductance in henries

Answer 91

Compete with capacitors for filtering and phase shift application Have fewer applications than capacitors because they are larger, heavier and more expensive

Answer 92

Inductors provide a reactive effect while still completing a DC circuit path Capacitors provide a reactive effect, but block the DC elements Inductors and capacitors are sometimes combined to improve the performance of a circuit The effects of pure inductance or capacitance cause the voltage and current to be 90 degrees out of phase. ELI (inductor) the ICE (capacitor) dude

Answer 93

The frequency above or below the frequencies passed or attenuated is called the cut-off frequency Symbol is fco can be determined by the formula fco = R / 2π * fL L = inductance in Henries

Answer 94

When an AC voltage source is applied, the instantaneous value of current flowing through the resistor varies with the alternating output voltage applied. Ohm's law applies Peak current calculated from the source peak voltage Rms current calculated from rms voltage Voltage: Vt2 = Vr2 + Vl2 Resistance: Zt2 = R2 + Xl2 Power: Pappt2 = Pr2 (true power) + Pl2

Answer 95

The combined effect of resistance and reactance Must be used to calculate current in a reactive circuit when the applied voltage is known Represented by the symbol Z The impedance of a parallel RL or RC circuit is smaller than both the individual resistance or reactance

Answer 96

Parallel circuits containing inductors and capacitors maybe analyzed with vector diagrams - Use current vectors - Voltage across each component must be equal and in place

Answer 97

In a purely resistive AC circuit - Obtain the average power -- Calculate the product of the rms current and rms voltage Power factor - The ratio of true power in watts to apparent power in volt-amps

Answer 98

A resonance device produces a broadening and dampening effect Resonant circuits pass desired frequencies and reject others Occurs when a circuit's inductive and capacitive reactance are balanced Xl = Xc Resonant circuit - Both inductive and capacitive components at the same frequency -- Reactances are equal but opposite - Used with radio frequencies in tuning receivers and transmitters - Not used in the audio bands of frequencies

Answer 99

The action caused when two electrically isolated coils are placed next to each other and an AC voltage is put across one coil. Resulting in a changing magnetic field which induces a voltage into the second coil. The device used to create this action is called a transformer The coil containing the AC voltage is the primary winding. The coil in which the voltage is induced is the secondary winding The design of a transformer is determined by - The frequency at which it will be used -- Low -frequency, iron cores -- High frequency, air cores - The power it must handle - The voltage it must handle Transformers are rated in volt-amperes Transformers are wound with tapped secondaries - Center tapped secondary is equal to two secondary windings - Used for power supply to convert AC voltages to DC voltages.

Answer 100

A number from 0 to 1 The coupling coefficient is defined as the fraction of the magnetic flux produced by the current in one coil that links with the current in the other coil.

Answer 101

Determines whether a transformer is used to step up (greater than one), step down (less than one) or pass voltage unchanged (Isolated transformer) The number turns in the secondary winding divided by the number of turns in the primary winding Expressed as turns ratio = Nsec / Nprim Where N = number of turns Either step up or step down, power is the same. Impedance ratio is equal to the turns ratio squared - Zp / Zs = Np2 / Ns2

Answer 102

Three pure semiconductor elements - Carbon C - Germanium Ge - Silicon Si most commonly used

Answer 103

The process of sharing valence electrons, resulting in the formation of crystals

Answer 104

As the temperature increases, its resistance decreases For silicon, resistance cuts in half every 60 C rise in temperature

Answer 105

The absence of an electron Represents the loss of a negative charge Therefore, it has the characteristics of a positively charged particle Each corresponding electron and hole are referred to as an electron-hole pair Holes constantly drift toward the negative terminal of the voltage source. Electrons flow toward the positive terminal Current flow in a semiconductor consists of the movement of both electrons and holes The amount of current flow is determined by the number of electron-hole pairs

Answer 106

A process to increase conductivity Doping is the process of adding impurities to a semiconductor material - Pentavalent, atoms with five valence electrons -- N-type material --- Has more electrons than holes --- Negative charge is the majority carrier --- Free electrons flow toward the positive terminal - Trivalent, atoms with three valence electrons -- P-type material -- Has more holes than electrons --- Positive charge is the majority carrier --- The holes move toward the negative terminal Diodes, created by joining N and P-type materials together

Answer 107

Junction diodes are created by joining N-type and P-type materials together The depletion region is the area near the junction The charge at the junction creates a voltage called a voltage barrier Current flows through a diode only when the external voltage is greater than the barrier voltage A diode that is forward-biased conducts current A diode that is reverse-biased conducts only a small leakage current A diode is a one-directional device The arrow on a diagram means the flow of holes P-Type is called Anode N-type is called Cathode

Answer 108

A bipolar transistor is produced when a third layer is added to a semiconductor It can amplify power, current or voltage Also called a junction transistor or transistor Can be constructed of germanium or silicon (more popular) Consists of three alternately doped regions The regions are arranged two ways - P-type material is sandwiched between two N-type materials NPN transistor - N-type material is sandwiched between two P-type materials PNP transistor It has three points, emitter, base and collector current flows 100% in emitter and 99% in collector Transistors are identified by a number - Begin with 2N and up to four more digits - Identify the device as a transistor - indicate that it has two junctions The basic functions of a transistor are - to provide current amplification of a signal - to switch a signal A transistor must be properly biased - The emitter junction is forward-biased - The collector junction is reverse-biased

Answer 109

A unipolar transistor that functions using only majority carriers Voltage operated Constructed from N-type and P-type semiconductor materials Capable of amplifying electronic signals JFETs have three electrical connections - One lead is connected to the substrate to form the gate (G) - One lead is connected to each end of the channel to form the source (S) and the drain (D) JFET requires external 2-bias voltages to operate - One is connected between the source and the drain, forcing the current to flow through the channel - One is connected between the gate and the source, controlling the amount of current flowing through the channel The side of the depletion region is controlled by the voltage gate-source - As the voltage increases, so does the depletion region - As the depletion region increases, the size of the channel is reduced, thus reduces the amount of current flow and can be used to control drain flow The amount of gate to source voltage required to reduced the drain current to zero is the gate to source cut off voltage The drain to source voltage has control over the depletion region within the JFET - As the voltage increases, so does the current - A point is reached where current levels off, even though voltage still increases - The value of the drain source voltage required to pinch off or limit the drain current is called pinch off voltage

Answer 110

Do not use PN junction Use a metal gate - electronically isolated from the semiconductor channel by a thin layer of oxide - Two important types of MOSFETs -- N-type units with N channels --- Called depletion mode devices --- They conduct when zero bias is applied -- P-type units with N channels --- Called enhancement mode devices --- Electron flow is cut off until it is aided or enhanced by the bias voltage on the gate

Answer 111

Three terminals - anode - cathode - gate Used primarily as switches Controls current in only one direction A power transistor would require ten times the trigger signal of an SCR to control the same amount of current Constructed of four alternately doped semiconductor layers - Three junctions are formed A small gate current can control a large load current

Answer 112

Electronic circuits used to increase the amplitude of an electronic circuit Amplifier configuration - The transistor can be connected in 3 different circuit configurations -- The common base circuit -- The common emitter circuit -- The common collector circuit - One lead serves as a common reference point and the other two leads serve as input and output connections - Each configuration can be constructed using NPN or PNP transistors - The transister's emitter base junction is forward biased - The collector base junction is reverse biased - The common emitter circuit is the most widely used, 180 degree phase shift