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Electrical Theory [FINALIZED!] > [D2L] Final Exam > Flashcards

[D2L] Final Exam Flashcards

(66 cards)

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1
Q

If we are checking ohms on a normally closed switch when the 120v system is energized and the ohm meter is flashing OL, what is happening?

A

Silly apprentice, turn the power off or check with the meter turned to voltage

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2
Q

Soft Iron has

A

High permeability and low reluctance to magnetic flux

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3
Q

What does it mean if your meter is reading a negative number?

A

the meter is connected in reverse polarity to the DC circuit

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4
Q

The effect that current has on a human body depends on four factors, which of these are NOT one of those factors

Area of contact
Pressure of contact
Improper grounding
Skin resistance

A

Improper grounding

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5
Q

How many current paths are there in a parallel circuit?

A

more than 1

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6
Q

DC transformers are commonly used to drop high voltage to low voltage?

A

False, Transformers only work with alternating current (AC)

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7
Q

an alternator converts…………………, into…………………… energy

A

mechanical, electrical

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8
Q

What would the total current be in a circuit with a 20vdc power source and a total resistance of 43ohms

A

0.47 A

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9
Q

What would the total resistance in a circuit be if there were 6.2 amps flowing from a 41 vdc power supply?

A

6.61 ohms

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10
Q

What would the power supply voltage be of a 47ohm circuit drawing 6.70 amps?

A

315 V

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11
Q

Which of the following is NOT a method of producing emf?

A

Radiation

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12
Q

Kirchhoff’s current law states:

A

All current values entering a junction point must equal all current values exiting the junction point

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13
Q

Three factors which contribute to impedance are

A

Resistance, inductive reactance and capacitive reactance

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14
Q

increasing the flow of current through a coil will..

A

increase the strength of the magnetic field

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15
Q

How is inductance defined?

A

The characteristic of an electric circuit that opposes a change in Current

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16
Q

In circuits with primarily capacitive loads, current leads the voltage

A

True

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17
Q

The CSA Z462 specifies workplace electrical safety

A

True

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18
Q

What is voltage drop?

A

When current flows through any conductor, there is a reduction in the EMF

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19
Q

What is the unit of measurement for a Charge?

A

Coulomb

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20
Q

Electron flow in a circuit travels from positive to negative

A

False

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21
Q

A Category II (CAT II) meter is safe to use on RACM equipment

T or F

A

False

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22
Q

Megohmmeters generate high voltage, low current signals to test insulation resistance. For test voltages at 500 VDC the minimum insulation resistance is ____

A

1 MO (megohms)

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23
Q

A conductor moving parallel to lines of magnetic force produces:

A

Minimum EMF

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24
Q

if the RPM of an alternator increases, then the output frequency of the alternator

A

Increases

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25
What electrical charge is the basis for a precipitation-type of air filter?
electrostatic
26
Which of the following are required to form a magnetic domain?
magnetic moments
27
Inductance is the property of an electrical circuit where a current change forces the rise of a voltage flowing in the reverse direction of the incoming voltage T or F
True
28
What is the positive plate called on a battery?
Cathode
29
The number of turns on the primary and secondary coils determines the amount of the mutually induced secondary coil voltage.
True
30
Which source of EMF is at work when you plug your radio into a wall receptacle?
Magnetic
31
Single conductors may have a Max load of 80% of the rated 15A T or F
True
32
What is flux density?
The number of lines of force passing through a unit area of material
33
the emf that is induced in a circuit by electromagnetism, is proportional to the rate of change of flux linkage. this statement could be used to summarize?
faraday's law
34
What amount of current is enough to kill a person?
100 to 200 mA
35
Current measurement is in Amperes how many mA are in one A?
1,000
36
What is the main purpose of a lockout system while working on electrical systems?
To prevent equipment from being energized while someone is working on it.
37
What is electromagnetism?
The interaction of the forces that electric fields and magnetic fields create
38
How is alternating current generated?
By moving wires through a magnetic field.
39
When any force squeezes a crystals made from bone, wood, metal or minerals the material compresses and produces electricity, this is called...
Piezoelectricity
40
what is the FIRST thing that must be done if an electrical shock occurs?
remove the victim
41
when illuminated, an incandescent light bulb will have a magnetic field close to the filament (glowing coil)? T or F
True
42
An averaging meter is the same as an RMS Meter T or F
False
43
ferromagnetic materials, like iron, allow magnetic flux to pass through them easily because they have a high
permeability
44
Soft Iron has a low reluctance which will concentrate magnetic flux more easily than air T or F
True
45
A capacitor has negatively and positively charged sections separated by a
Dielectric
46
An ECM motor stands for electronically commutated motor
True
47
According to the left hand conductor rule, when your thumb is up, the.......
electrons travel the direction your thumb is pointing, with a rotating magnetic field pointing in the direction of your fingers around it
48
Which metric is most accurate to prove work is actually being done Voltage detected at the load Amp draw is detected at the load
Amp draw is detected at the load
49
What is the vdc power source of a 2.0 amp series circuit with a 9, 4, 6, 10 ohm resistors
58 V
50
What is the current of a 120 vdc series circuit with a 7, 10, 8, 8 ohm resistors
3.64 A
51
Yesterday you were repairing a 210 vdc power source of a 2.0 amp series circuit, when you returned this morning you found one of your 5 resistors was burned beyond recognition. Calculate the missing resistor if you were left with a 15.0, 7.0, 11.0, 12.0 ohm resistors.
60 ohms
52
Using heat to produce electricity is the process known as
Seebeck Effect
53
if Emax is 120V what is the instantaneous value at 60*?
103.92 vac
54
what would the instantaneous voltage value be at 30* angle of the sine wave of a system with 169.7V Peak voltage
85 vac
55
What frequency of ac power is being generated from an alternator spinning at 3600rpm with 2 poles?
60 hz
56
What is the rpm of a 120vac 36 hz. motor with 4 poles?
1080 rpm
57
What is the maximum peak voltage of a 224 vac rms power system?
317 v
58
What is the effective voltage of a sine wave that peaks at 130 vac?
92 v
59
A 4 pole alternator rotates 3 times, producing how many electrical degrees?
2160
60
What are two classifications of Magnets?
Temporary and Permanent
61
What is the unit of measurement for inductance?
Henry (H)
62
360° in an electrical sine wave is also known as what?
a cycle
63
one of the 3 factors that determine the severity of an arc flash is
the time it takes the circuit breaker to open
64
which of these are not likely to significantly increase the probability of an arc flash?
LED lights
65
What do you read with your voltmeter?
Effective value
66
What happens if there is a loose or poorly made electrical connection? A drop in amperage A drop in resistance A drop in voltage
A drop in voltage

Electrical Theory [FINALIZED!] (18 decks)

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