Master Electrician Flashcards
What is an ampere?
The unit of current measurement. The amount of current that will flow through a one ohm resistor when one volt is applied
How do you find Power?
Power(P) = Current(I)x Volts(E)
How do you find Current?
Current(I)=Power(P) / Volts(E)
How do you find Volts?
Volts(E)= Power(P)/ Current(I)
I stands for?
I = Amperes or Current draw on the load
E stands for?
E = Volts
kVA stands for?
kVA = Kilovolt-Amperes
PF stands for?
PF = Power Factor
HP stands for?
HP = horse power
VA stands for?
VA = Power
W stands for?
W = Watts
Pf stands for?
Pf = Power Factor
How do you find VA (power)?
VA = W watts/Pf power factor
Ohms Law Circle Formula uses what 3 letters?
E. I. R. E(Voltage). I(Current). R(Resistance)
Power Circle Formula uses what 3 letters?
P. I. E. P(power) I(Current). E(Volts)
Power Factor Triangle uses what 3 letters?
W. VA Pf. W(watts). VA(Power). Pf(Power Factor)
How do you find Resistance?
Resistance(R) = (E)Voltage/(I)Current
How do you find Current?
Current(I) = (E)Voltage/(R) Resistance
How do you find Voltage?
Voltage(E) = (I)Current x (R) Resistance
What is the multiplying factor(number) consistently used in three phase formulas?
1.732
How do you find Watts?
Watts(W) = VA (Power) x Pf (Power Factor)
How do you find Pf?
Power factor(Pf) = (W)Watts / (VA) Power
VD stands for?
VD = Volts dropped from a circuit
What is the multiplying factor for a single phase circuit?
2, The 2 represents the conductor length in single-phase circuits
What does D stand for?
D = The distance from the source voltage to the load
What does K stand for?
K = is the resistivity of the conductor per mil foot. A mil foot is a wire 1 foot long and one mil in diameter.
The K value of Copper - 12.9 ohms per mil foot
The K value of Aluminum - 21.2 ohms per mil foot
What is the K value of Copper per mil foot?
12.9 ohms
What is the K value of Aluminum per mil foot?
21.2 ohms
What is the formula to find voltage drop in a single phase circuit?
VD = 2 x K x I x D / CM
What does CM stand for?
Circular mil area of a conductor (refer to chapter 9/table 8)
How do you find wire size in a single - phase circuit? (formula)
D = CM x VD / 2 x K x I
How do you find the MAXIMUM current in amperes in a single - phase circuit? (formula)
I = CM x VD / 2X K X D
One kW equals how many watts?
1000
One kVA equals how many volt-amps
1000
One horse power equals how many watts?
746
What is the formulas used to determine the available power for a single phase circuit, load, or an electrical system?
P = I x E P = current x volts P = volts x amps
Current can be expressed as …
as the letter I and as... amps amperes full-load current amperage amperage draw line load FLC FLA full load amps
Power factor is the ratio between true power expressed and ___________?
watts, kilo watts kW volt-amps VA kVA
True power (watts) EQUAL to apparent power (VA) in …..
an electric circuit or load containing ONLY resistance
True power (watts) is LESS than apparent power (VA) in a circuit or load containing …
inductance or capacitance, such as motor, transformers, HID and florescent lighting
What is the definition of a CONTINUOUS load?
Where the maximum current is expected to continue for 3 hours or more
Examples of a continuous load are …..
Lighting loads (commercial and industrial occupancies) expected to operate for 3 hours or more.
Branch circuit conductors shall have an allowable ampacity of NOT less that …
125% of the continuous load, plus the 100% of the non-continuous load
How is the rating of a branch circuit determined?
By the maximum ampere rating of the overcurrent protective device (circuit breaker or fuse) and NOT by the size of the conductors used for the branch-circuit
True or False: Circuit breakers are NOT listed for continuous operation, unless they have a rating of at least 400 amperes or more.
True
True or False: In general, lighting loads are to be supplied by 15- and 20- ampere rated branch circuits
True
True or False: Overcurrent devices protecting branch circuits are not to be loaded more than 70% of their rated value when protecting continuous loads.
False - 80%
When calculating lighting loads for dwelling units DO NOT include…
open porches, garages, or unfinished spaces not adaptable for future use.
True or False: Lighting loads for habitable spaces of dwelling units and guest rooms and hotels and motels are considered as continuous use.
FALSE - guest rooms and hotels and motels are NOT considered as continuous use BUT lighting loads of commercial and industrial occupancies ARE considered as continuous.
True or False: Multifamily condo without a cooking facility is calculated at the same 2 VA per square foot as hotels and motels when determining the minimum general lighting branch-circuits.
True
