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Third Year > Electrical Principals > Flashcards

Electrical Principals Flashcards

1
Q

EMF

A

Electromotive force - the voltage developed by any source of electric energy

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2
Q

Conductor, Insulotor, semi-conductor

A

conductor -materials that exhibit low resistance to current flow like silver, copper, gold, aluminum Insulator -materials that exhibit high resistance like glass, mica, dry woods and plastics Semiconductor -neither good nor bad conductor (silicon and germanium. By contaminating/doping a semi conductor you can increase its conductivity.

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3
Q

Electromagnetism

A

-fundamental force of nature which consists of electricity and magnetism -the interactive relationship between electric charge and magnetic flux

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3
Q

Electric charge

A

-the force protons and electrons exert

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4
Q

Principles of electromagnetism

A

-moving electrically charged particles create magnetic fields -magnetic fields attract or repel moving charged particles -moving magnetic fields near charged particles causes current flow

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5
Q

Resistance

A

-the difficulty to pass an electric current through a conductor

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6
Q

Current Flow

A

When electric charges move through a conductor

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7
Q

Voltage

A

-basically electrical pressure (similar to hydraulic pressure) -for electric current to flow there must be a difference between two points of the supplying device -a one volt potential difference causes one ampere of current to flow through a resistance of one ohm. Symbol used in math is “E”. -the potential difference between the positive and negative terminals of a battery causes current flow

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8
Q

Amperes

A

-rate of flow of electrons (current flow) in an electrical circuit -one amp flows when an EMF of one volt is applied across a resistance of one ohm. Symbol in math is “I”. Induced or force -compatible to rate of flow in hydraulics -measured in current flow

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9
Q

Frequency

A

-the number of cycles an alternating current generates per second -standard power line frequency is 60 cycles per second or 60 hertz

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10
Q

Hertz

A

-unit of frequency which is one cycle per second -number of times the current is refreshed (turned on/off) per second

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11
Q

Electric Current

A

-direct current - the flow of free electrons in the conductors of the circuit all flowing the same direction

Direct current has fixed polarity

-alternating current is when the flow changes direction continuously and regularity.

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12
Q

Direct Current Uses

A

-charging rechargeable batteries -operating electronic equipment -operating dc motors -welders -industrial electromagnets

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13
Q

Polarity

A

-direction of current flow -when the direction stays in the same direction it is fixed polarity as it is with direct current - it can be positive or negative -when it changes constantly as it does with alternating current it is called instantaneous polarity

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14
Q

Direct Current Sources

A

-portable welders -car battery -solar energy cells

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15
Q

Electrical Circuits

A

-the path an electric current follows - there can be open circuits when the path is incomplete because the switch is open -there is a closed circuit which is a complete circuit where there is nothing preventing the current from flowing through the entire circuit

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16
Q

Phases of power sources

A

-single phase and three phase are most common -phase indicates the relationship in time (in degree of rotation) between current and voltage -power sources deal with either a single time frame for voltage or more than one time for more than one voltage

17
Q

Single phase

A

-a single voltage (rising and falling potential) that creates a potential difference between two conductors

18
Q

Series Circuits

A
  • when they are connected end to end or in tandem
  • total voltage in a series circuit must add up to each component connected in the series and all voltage is used up before it gets to the end of the line
  • remember to think math when reading each question even if its not an equation cause the triangle help answers about voltages, etc…
19
Q

Three Phase

A

-three different voltages that interact to produce potential differences between the three conductors that supply the three phase loads

20
Q

Watts

A
  • one amp per second flowing under the potential difference of one volt.
  • 746 watts = 1hp
  • watts = amps x volts
21
Q

Watt’s Law Triangle

A
  • “P” power in watts
  • “I” current in amps
  • “E” EMF or volts
23
Q

Electrical Power

A

-can be transformed from potential energy to kinetic or electrical to mechanical -the rate of doing work measured in watts

24
Q

Uses for alternating current

A

-power transmission and distribution -residential, commercial and industrial power

25
Q

Alternating current sources

A

-hydroelectric dam -gas powered alternator -automotive alternator -electric investor

26
Q

Magnetic Flux

A

-the entire magnetic field surrounding a magnet

27
Q

Sine wave

A

-when a conductor in an alternating current generator passes completely passes completely by a north and South Pole of the generator and the value of the voltage is plotted on a graph

28
Q

RMS

A
  • usable power you are getting out of it
  • root mean square
  • Equivilent production of heat in a resistive load of a dc current.
29
Q

Cycles

A

-sine wave starts from 0 volts, reaches a peak at 90* of rotation in the positive direction and drops back down to 0 volts at 180*. It then goes to a peak in the negative direction at 270* and then returns to 0 volts at 360* of rotation

30
Q

Capacitors

A

-stores the energy until it’s needed (car battery)

31
Q

Ohm’s Law

A

-“E” stands to EMF (volts) -“I” stands for current (amps) -“R” stands for resistance (ohms)

32
Q

Factors affecting resistance

A

-materials -cross sectional area -length of conductor -temperature

33
Q

Factors affecting Inductance

A

-material -frequency -amp turns (number of wraps of wire around the coil

34
Q

Capacitance

A

-same as a hydraulic accumulator -two conductors separated by an insulators form a capacitor -a capacitor stores electrical energy in an electrostatic field.

35
Q

Inductance

A

-

36
Q

Series Circuit Math

A

-

37
Q

Electron Flow

A

-Current flow from a negatively charged body to a positively charged body

38
Q

Parallel Circuit Math

A

-

39
Q

Parallel Circuits

A
  • parallel or divided circuit where the current can flow to the one branch and back or to the other branches but only one at a time
  • the more resistors you add, the less resistance the circuit has which allows the current to increase
  • the total voltage of the circuit will be used up as it goes throw each branch and comes back to the beginning.
40
Q

Magnetic pole attraction and repulsion

A

-earth’s north pole and a magnet’s north pole are opposite polarity.

Third Year (21 decks)

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