ACM-105 FINAL EXAM Flashcards by Tim Lankford

Voltage is considered _____.

Potential

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What is the symbol for voltage?

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What is the symbol for voltage?

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What does voltage (E) do in a circuit?

Pushes current.

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The force that causes electrons to flow is called _____.
What is it measured in?

Electromotive force (EMF)
volts

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What else is voltage referred to?

potential

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If you have potential difference in 2 conductors, what would you use to measure it?

volts

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Resitance is measure in _____.
Potential is measured in _____.
Current flow is measured in _____

Ohms
Volts
Amps

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Ways to lower the resistance of a conductor.

Increase the diameter
Increase the cross sectional area.
Decrease the length
Change the material

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What is the purpose of a thermal switch on an electric motor?

isolate motor from circuit if it overheats

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A circuit breaker is designed to _____.

protect the wire

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What is the purpose of a ground symbol in a schematic?

shows the return path for current

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If you have 3 resistors in series with a 24v battery, how much current would be flowing through each resistor?

?
4 miliamps

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(3-57)
What is the purpose of this chart?

Temperature correction for battery acid.
Indicates the correction for acid specific gravity

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At what temperature is no correction required?

80°

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If charging a battery using the constant current method, what determines the amount of current that will flow in to the battery?

Resistance of the battery, related to the state of charge of the battery determines the current will flow.

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Are potassium carbonates acceptable when charging a NICAD battery?

Yes. They are part of the charging process.

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When do you check the electrolytes liquid level of a NICAD battery?

When fully charged.
When charging it drives the electrolytes out of the plates.

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The end charge of a 19 cell NICAD battery measured when still uncharged should be charged to what voltage will charge it by depend on?

Temperature the battery is charged at
Method used for charging (Constant current / Constant voltage)

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Why would you charge a NICAD battery to 110%

To eliminate the cell imbalance

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What is the purpose of a capacitor used in a DC circuit?

Smooth out the pulsating

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How many amps is .001 amps?

1 milliamp

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P -
I -
E -
R -

Watts
Current
Volts
Resistance

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If you were to spill electrolyte from a lead acid battery, what would you clean it with?
What does it do to the acid

Sodium bicarbonate.
Neutralizes the acid

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If you were to spill electrolyte from a NICAD battery, what would you clean it with?

boric acid / vinegar

In extreme cold better to have lead acid battery charged or discharged?

charged

If you have arcing on a NICAD battery what would be the cause of it?

loose connections

How do you check the state of charge of a NICAD battery?

Measured discharge - capacity check. Amps / temperature / size of battery. Make sure no cells go reverse polarity

The advantage of a NICAD battery

holds voltage constant until almost dead Has very little resistance

How many electrons are in a conductor? How many electrons are in an insulator?

1-3 5-8

What is the prefix and symbol for the following multiplier? 1,000,000,000,000

tera t

What is the prefix and symbol for the following multiplier? 1,000,000,000

giga g

What is the prefix and symbol for the following multiplier? 1,000,000

mega M

What is the prefix and symbol for the following multiplier? 1,000

kilo k

What is the prefix and symbol for the following multiplier? 100

hecto h

What is the prefix and symbol for the following multiplier? 10

deka dk

What is the prefix and symbol for the following multiplier? 0.1

deci d

What is the prefix and symbol for the following multiplier? 0.01

centi c

What is the prefix and symbol for the following multiplier? 0.001

milli m

What is the prefix and symbol for the following multiplier? 0.000,001

micro µ (mu)

What is the prefix and symbol for the following multiplier? 0.000,000,001

nano n

What is the prefix and symbol for the following multiplier? 0.000,000,000,001

pico p

Which metric prefixes are used extensively in the study of electricity?

pico micro milli kilo

What are the 5 sources of electricity?

1. Chemical 2. Thermal 3. Pressure 4. Light 5. Magnetism

What is permeability?

The ease of which it accepts lines of magnetic flux.

What is retentativity?

How long it holds its magnetism after the magnet has been removed.

What 3 things are needed to complete a circuit?

1. Source of electrical energy - Battery 2. Load device 3. Conductor

What is the purpose of a fuse?

To protect the wiring (not the device) from overheating because of excessive current flow.

Know the color bands of resistors.

First band - First figure Second band - second figure Third band - Multiplier Fourth Band - Tolerance Tolerance - No color - 20%

Know chart on page 3-22

What device changes DC to AC?

Inverter

What changes AC to DC?

Rectifier

Study 3-35 to 3-38

What is the difference between a primary and a secondary cell?

Secondary cell can be recharged. Primary cell consumes the material and cannot be recharged.

If a battery has an open cell voltage of 26 volts? Terminal voltage supplying 20 volts What is the internal resistance? 3-57

Voltage drop in a battery is an indication of what?

It is a lead acid battery. As the battery discharges and the volts drops, the internal resistance goes up.

What is the allowable current limit between the battery cells and the steel case? What does this indicate? 3-63

100 milliamps Electrical leakage - discharging

What determines the size of the conductor you need to use?

Amount of current needed

A generator with 10 poles rotating at 1000 rpm, what would the frequency be?

of poles divided by 2 RPM divided by 60. 10 1000 _____ X ________ 2 60

A sine wave with peak voltage of 165 volts, what would the effective value be?

.707 X voltage

L - Inductive ELI the ICE Voltage leads current in inductive Current leads the voltage in a capacitive circuit

Total capacitance Total Inductive both series and parallel circuits. Verify formulas on sheet

10 mhenry conductor connected to 600 hz AC what is the opposition of the coil? If the frequency goes up, ohms goes up. (3-77)

XL = 2πfL 3.1416 X 2 X 600 X .01 XL - (ohms)

What is the formula for apparent power?

Total voltage X current

Calculate total resistance 2 resistors in a parallel AC circuit operating at 120 volts 600 hz Resistor - 60 ohms Resistor - 120 ohms (3-87)

60 X 120 7200 ___________ ________ 60 X 120 = 180

What is the power factor Power apparent 250 v Power True - 150 w (3-88)

150 / 250 = 60%

Page 3-89 Said he would give us this question

3 Phase alternator the phases are how far out of phase?

120°

In 2 phase in a Y 3 phase circuit voltage across 2 phase windings of 208 volts is how many volts across the Y? (3-92,93)

120 volts

What does the term short circuit mean?

Calculate this circuit.

Calculate this circuit