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From Flashcardlet > basic electric > Flashcards

basic electric Flashcards

0
Q

What is the purpose of a capacitor

A

It stores electrical energy in electrostatic fields

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1
Q

What constitutes a capacitior?

A

Two conductors separated by an insulator.

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2
Q

Does a capacitor in a AC circuit cause the current to lead or lag the voltage?

A

It causes the current to lead the voltage

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3
Q

What is the basic unit of capacitance?

A

The farad

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4
Q

Why should electrolytic capacitor not be used in an AC circuit?

A

They are polarized. An electrolytic capacitor will pass current of one polarity, but will block current of the opposite polarity

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5
Q

What is meant by inductances?

A

The ability to store electrical energy in electromagnetic fields

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6
Q

What is the basic unit of inductances?

A

The henry

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7
Q

What is an example of an inductor used in a magneto?

A

The coil

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8
Q

Does an inductor in an AC circuit cause the current to lead or lad the voltage?

A

It causes the current to lag behind the voltage

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9
Q

How can you fine the polarity of an electromagnet?

A

Hold the electromagnet in your left hand with your fingers encircling the coil in the direction electrons flow from (negative to positive). Your thumb Well point to the north pole of the natural magnet

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10
Q

What is meant by impedance?

A

The total opposition to the flow of alternating current. It is the vector sum of resistance, capacitive reactance and inductive reactance

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11
Q

In what unit is impedance measured?

A

In ohms

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12
Q

What are five source of electrical energy?

A

Magnetism, chemical energy, light, heat, and pressure

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13
Q

What is the basic unit of power in a DC circuit?

A

The watt

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14
Q

What is meant by a kilowatt

A

1,000

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15
Q

What is meant by a megawatt

A

1,000,000 watts

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16
Q

What is the formula for power in a DC circuit?

A

Power = voltage times current (P = E • I

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17
Q

What is the relationship between mechanical and electrical power?

A

1 horsepower = 746 watts

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18
Q

What is meant by true power in an AC circuit?

A

The products of the circuit voltage and the current that is in phase with this Voltage.

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19
Q

In what unit is true power expressed?

A

In watts

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20
Q

What is meant by apparent power in an AC circuit?

A

The product of the circuit voltage and the circuit current.

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21
Q

And what unit is apparent power expressed?

A

In volt-amps

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22
Q

What is meant by reactive power in an AC circuit?

A

The power consumed in the inductive and capacitive reactances in an AC circuit. Reactive power is also called Watless power.

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23
Q

And what unit is reactive power expressed?

A

In volt –amps reactive (DAR), or kilovolts –amps reactive (KVAR).

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24
Q

What is meant by power factor in an AC circuit?

A

The ratiol of true power to apparent power. It is also the ratio of circuit resistance to circuit impedance.

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25
Q

Which law of electricity is the most important for an aircraft mechanic to know?

A

Ohm’s law

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26
Q

What are the elements of Ohm’s law?

A

Voltage E, current I, and resistance R (volts,amps, ohms)

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27
Q

What is voltage?

A

Electrical pressure

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28
Q

What is the basic unit of voltage?

A

The volt

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29
Q

What instrument is used to measure voltage

A

A voltmeter

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30
Q

To measure voltage, is a voltmeter placed in series or in parallel but the source of voltage?

A

Parallel

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31
Q

What is electrical current?

A

The flow of electron in a circuit

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32
Q

What is the basic unit of current flow?

A

Ampere (amps)

33
Q

What part of amp is a milliamp?

A

One thousands (0.001 amps)

34
Q

What instrument is used to measure current flow?

A

An ammeter

35
Q

What two things happen when current flows through a conductor?

A

Heat is generated and a magnetic field surrounds the conductor.

36
Q

To measure current through a component, is it ammeter place in parallel or in series with the component?

A

Series

37
Q

What is meant by resistance in an electrical circuit?

A

The opposition to the flow of electrons

38
Q

What is basic unit of electrical resistance?

A

The ohms

39
Q

What is a megohm?

A

One million ( 1,000,000) ohms.

40
Q

What four things affect the resistance of an electrical conductor?

A

The material, the cross-sectional area, the length, and the temperature.

41
Q

What instrument is used to measure electrical resistance?

A

An omhmeter

42
Q

How can you tell the resistance of a composition resistor?

A

By a series of colored bands around one end of the resistor.

43
Q

What is meant by continuity in an electrical circuit?

A

The circuit is continuous (or complete) when the electrons can flow from one terminal of the power source to another.

44
Q

What instrument is used to measure continuity in an electrical circuit?

A

An ohmmeter

45
Q

When measuring the resistance of a component with an ohmmeter, should the circuit be energized?

A

No, there should be no power on the circut.

46
Q

What three things must an electric circuit contain?

A

A source of electrical energy, a load to use Energy, and conductors to join the source and the load.

47
Q

What are three types of DC circuits with regard to the placement of the various circuits components?

A

Series, parallel, and series – Parrallel

48
Q

What is the name of the law that describes the relationship in an electrical circuit voltage, current and resistance?

A

Ohm’s law

49
Q

What is the basic equation of ohm’s law?

A

E = I • R

50
Q

What formula is used to find current when voltage and resistance are known?

A

I = E / R

51
Q

What formula is used to find resistance when voltage and current are knowing?

A

R = E / I

52
Q

What happens to the current in a DC circuit if the voltage is increased but the resistance remains the same?

A

Current increase

53
Q

What happens to the current In a conductor if the length of the conductor is doubled with all other parrameters unchanged?

A

Current would decrease to one half

54
Q

What is the voltage across each resistor connected in parallel across a 12-volt battery?

A

12 volts

55
Q

How much current flows to each of the three resistors connected in series if the.total current is 3 amps?

A

3 amps

56
Q

What is the total resistance three 12ohms resistors connected in series?

A

36 ohms

57
Q

What is the total resistance of three 12 ohms resistors connected in parallel?

A

4 ohms

58
Q

What is meant by the capacity rating of a lead-acid battery?

A

The number of hours a battery can supply a given current flow

59
Q

In what unit is battery capacity express?

A

In ampere-hours

60
Q

What electrolyte is used in a lead – acid battery?

A

A mixture of sulfuric acid and water

61
Q

Does the specific gravity of the electrolyte and it lead- acid battery increase or decrease as the battery becomes discharged?

A

Specific gravity decreases

62
Q

What is the specific gravity of a fully charged lead – acid battery?

A

Between 1.275 and 1.300

63
Q

How many cells are there in a 24-volt lead – acid battery?

A

12 cells

64
Q

What is the range of temperatures of the electrolyte in a lead – acid battery that does not require a correction when measuring its specific gravity?

A

Between 70 degrees F and 90 degrees F

65
Q

What instrument is used to measure the specific gravity of the electrolytes in a lead acid battery?

A

A hydrometer

66
Q

How do you treat a lead- acid battery compartment to protect it from corrosion?

A

Paint it with an asphaltic (tar-base) paint or with a polyurethane enamel.

67
Q

What is used to neutralize spilled electrolyte from an lead acid battery?

A

A solution of bicarbonate of soda and water

68
Q

How high should the electrolyte level Be in a properly serviced lead – acid battery?

A

Only up to the level of the indicator in the cell

69
Q

What is the closed– circuit voltage of a lead – acid battery Lower then it’s open - circuit voltage?

A

Voltage is drop across the internal resistance of the battery

70
Q

What is the open – circuit voltage of a lead – acid cell?

A

2.1 voltage

71
Q

What gases are released when a lead-acid battery is being charge?

A

Hydrogen and oxygen

72
Q

What precautions should be taken in the maintenance shop where both lead-acid and Nickel- cadmium batteries our service?

A

The two types of battery should be kept separate, and the tools use on one type should not be used on another.

73
Q

What is the electrolyte used in a Nickel – cadmium battery?

A

Potassium hydroxide and water

74
Q

What is a Hydrometer not used to measure the state of charge of a nickel – cadmium battery?

A

The electrolyte of a nickel – cadmium battery does not enter into the chemical changes that occurs when the battery is charged or discharged. It’s specific gravity does not change appreciably.

75
Q

Is the electrolyte levels of a nickel – cadmium battery lowest when the battery is fully charged or fully discharge?

A

Fully discharged

76
Q

What is a result of cell imbalance in a nickel – Cadmium battery?

A

The low internal resistance allows current to flow between the unbalanced cells and generate heat

77
Q

What is thermal runaway?

A

The large current flows allowed by the little internal resistance causes the middle cells to produce more heat than they can dissipate. The heat further lowers the internal resistance so more current can flow; this continues until the battery destroys itself

78
Q

How may thermal runaway be prevented?

A

By carefully monitoring the temperature of the middle cells and controlling the charging current to prevent excess of current flowing into the battery

79
Q

How is it possible to know when a Nickel-cadmium battery is fully charged?

A

Completely discharged the battery and give it a constant-current charge to 140% of its ampere-hour capacity

80
Q

What is used to neutralize the electrolyte from nickel-cadmium battery?

A

A solution of boric acid and water

From Flashcardlet (3 decks)

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