Electrical Questions Test Flashcards
WHat does EMF stand for in electrical
Electromotive force
Is used to indicate electrical pressure or voltage.
“Potential difference”
What does A.C stand for?
Alternating Current
A.C is not constant, it’s going from negative to positive in a sine wave
What does R.M.S stand for?
Found on a multimeter.
Root Means Square
Modern multimeters calculate the actual Voltage using a formula.
What does Current define in a electrical system?
Is a measurement of the rate of flow or electrons.
What is a ampere in an electrical system?
An ampere is one coulomb of electrons flowing past a given point in one second.
One coulomb is aprox.
6,280,000,000,000,000,000 or 6.28x10e18 electrons
What is resistance in an electrical circuit?
Basically “Oppostion to the flow of electrons”
All material have some resistance to the flow of electrons.
What four things effect resistance in an electrical circuit?
1 Material(Aluminum vs Copper)
Diameter( 8awg vs 6awg)
Length (25’ vs 50’)
Temperature (60Celsuis vs 75 celsuis)
You connect an ammeter in ____ with the load?
Series/Parallel
Series
You connect a Voltmeter in____ across the load
Series/Parallel
Parallel
In a series circuit, how does resistance act?
Total resistance is added together.
(r1+r2+r3=RT)
In a series circuit, how does Amperage behave across each load?
The amperage is constant througout a series circuit.
i1=i2=iT
i = Amperage
In a series circuit, how does Voltage behave across each load?
The total voltage is equal to all the voltage drops across each load.
ET=E1+E2+E3
E=Voltage
In a parallel circuit, how does Resistance act?
Total resistance is less then the lowest sum in the circuit.
{1/(1/R1+1/R2+1/R3)=Rt}**
**Formula for finding resistance in parallel circuit
How does Voltage behave in a parallel circuit?
Voltage is constant across each load.
(Et=E1=E2)
Et= voltage total/Total Voltage
In relation to a parallel circuit, how will amperage act?
The Current total is all individual loads added together.
(I1+I2=It)
In a series circuit, if one component fails, what happens to the rest of the circuit?
The entire circuit stops working
If you add more resistors to a series circuit, the total resistance will:
Increase
In a series circuit, if the total voltage is 12V and there are three equal resistors, what is the voltage drop across each resistor?
4V
When calculating the total resistance in a series circuit, you should
Add them together
In a series circuit, the sum of the individual voltage drops across each resistor is?
Equal to the total voltage
If the current through a series circuit is 2A, and the resistance is increased, the current will
Decrease
In a series circuit with different resistors, the resistor with the highest resistance will have the_ _ _ _ _ Voltage Drop
Highest
In a parallel circuit, if one branch is opened or disconnected, what happens to the other branches?
The electrical service supplied to a building is measured in?
Watts
Watts=Power, Power=Watts
Homes which are heated by electricity require what size of service?
Amps
200Amps
Which gauge of wire is normally used for residential lighting and receptacles?
14/2 AWG
The GFCI will trip when it senses what change of current flow?
0.005 Amps
What size of grounding/bonding wire is used?
6 AWG
The voltage sine wave of a three-phase wire system is out of phase with each other by_ _ _ _ Degrees
120
360 Deg. divided in 3 = 120 degrees
Failure of a conductor’s insulation, causing the conductor to touch casing and create line-to-ground, is called a?
Short Circuit
You SHORT the CIRCUIT by going back to the source.
A current surge when a motor starts up is called
An Overcurrent
Motor pulling to many amp very quickly
The use of worn out or seized bearings in electrical equipment could cause
Overload
Pulling to many amps for far to long.
What color is a fuse rated for up to 15 Amps?
Blue
What color is a fuse rated for up to 20 Amps?
Red
What color is a fuse rated for up to 30 Amps?
Green
What is the maximum voltage considered to be a low voltage system?
When compared to power lines!
750V
The ability of a material to be drawn into wire form is called:
Ductility
When taking a voltage reading, how should the meter be connected?
In parallel with the load being checked.
A basic multimeter incorporates which electrical meters?
Voltmeter, Ammeter, Ohmmeter
What is the power rating of a secondary stage in a transformer if it has 24 volts and 10 amps?
240W
P=V*A
How many wires are contained in a service conductor to a residential panel?
From the road to the main breaker panel
2 Hot, 1 Neutral, 1 Ground
How are transformers rated?
Volt-Amps (VA)
The electrical code requires all electrical connections be
Where do you make a connection or ‘pig-tail’
Made in a junction or outlet box
Switches are located in which leg of the circuit?
Hot,
You want to interupt power going into the equipment.
Dangerous to do on the Neutral!!!!
Thermocouples generate DC voltage in which range?
0-30mV
When the pilot fails, the thermocouple must cool down and de-energize the safety shut-off valve or safety switch within:
180 seconds
Thermocouples are only approved for gas appliances with inputs up to and including:
How many Btu/H
400,000 Btu/H
A thermocouple only generates a voltage if the temperature difference between the hot and cold junctions is at least?
400°F
The pilot flame should only heat the first
How much should the flame cover in inches.
1/2”
Thermopiles generate a DC voltage of?
250mV-750mV
What is one non-desirable characteristic of a normal pilot flame?
A Hard, Sharp flame
The thermocouple should be replaced when a open test reading of what occurs?
0-15mV
