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CFESA Electrical Questions and Correct
Answers
What do the following prefixes mean? Micro,Kilo,Mega,Milli Ans:
— 1/1,000,000, 1000, 1,000,000, 1/1000
If you know the wattage and voltage, how do you determine the
current? Ans: — Divide the wattage by the voltage
If you know the voltage and current how do you determine the
wattage? Ans: — Multiply voltage times current
If a circuit is supplied with 100 volts and the total resistance of
the circuit is 200 ohms, how much current will the circuit draw?
Ans: — .5 amps
If a piece of equipment is supplied 208 volts and the amp meter
clamped to the hot line reads 20 amps, what is the wattage of the
load? Ans: — 4160 Watts
How much voltage is in one hot line? Ans: — None
What happens to current in a parallel circuit? Ans: — It divides
across resistances
what happens to voltage across the loads in a parallel circuit? Ans:
— stays the same
what happens to the voltage across the loads in a series circuit?
Ans: — it divides across the resistances
what happens to the current in a series circuit? Ans: — It stays the
same everywhere
in a parallel circuit the total resistance of the circuit will always be
less than what resistance? Ans: — the smallest resistance
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how do you find the total resistance of a series circuit? Ans: — add
the resistances together
how do you find the total resistance of a parallel circuit? Ans: —
1/RT = 1/R1 + 1/R2 + 1/R3 ...
If a circuit is wired parallel, and the supply voltage is 120 volts,
each load must be rated at what voltage? Ans: — 120 volts
if a circuit has two elements wired in series, and each is rated at
120 volts, what voltage must be supplied to the circuit in order for
the elements to heat at full power? Ans: — 240 volts
What is the advantage of using higher voltages? Ans: — Lower
Current and wire size
Is there a negative and positive line in AC power supplies? Ans: —
No
What is the voltage between two hot lines in a 230-volt system?
Ans: — 230V
What is the voltage between two hot lines in a 208-volt system?
Ans: — 208V
What is the voltage between a hot line and a neutral in a 230-volt
single phase supply? Ans: — 115V
What is the voltage between a hot line and a neutral in a 208-volt
single phase supply? Ans: — 120V
What is the accepted maximum voltage difference between the
name plate voltage and the supplied voltage? Ans: — + or - 10%
What is the voltage between any two hot lines of a 230 volt delta
power supply? Ans: — 230V
what is the voltage between a hot line and ground on a 240 volt
delta power supply Ans: — No usable voltage
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what is the voltage between any two hot lines of a 230 volt
grounded delta power supply Ans: — 230V
what is the wild leg? Ans: — leg with higher than 120v to ground
or neutral
what danger is the wild leg? Ans: — high voltage that will damage
120v component in the circuit
what is the voltage between either of the non wild leg hot lines and
neutral in a 230 volt grounded delta system? Ans: — 115v
how do you determine which hot line is the wild leg in a 250 volt
grounded delta power supply? Ans: — the one that does not
measure 120 volts to neutral or ground
what danger is there when replacing a three phase circuit breaker
in a 230 volt grounded delta power supply? Ans: — crossing the
hot lines and supplying the wild leg to the wrong terminal in the
unit.
Why is a "WYE" power supply so versatile Ans: — can get 120v and
208v as well as single and three phase
What is the voltage between any two hot lines in a 208 volt WYE
power supply? Ans: — 208v
What is the voltage between any hot line and neutral or ground in
a 208 volt WYE power supply? Ans: — 120v
What is the voltage from any hot line to ground or neutral, on a
480 volt WYE power supply? Ans: — 277v
if you had a commercial building and you had a three phase
supply to your building how many different incoming power
supplies would you need if the incoming three phase supply was
three phase delta? Ans: — 2
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if you had a commercial building and you had a three phase
supply to your building, how many different incoming power
supplies would you need if the incoming three phase supply was
three phase grounded delta? Ans: — 1
if you had a commercial building and you had a three phase
supply to your building how many different incoming power
supplies would you need if the incoming three phase supply was
three phase WYE 208v? Ans: — 1
approximately how much will the wattage increase on a 208v piece
of equipment if it is connected to 240v supply? Ans: — 33%
approximately how much will the rated wattage decrease if a 240v
unit is connected to a 208v power supply? Ans: — 25%
what damage could potentially be caused to the supply wiring if
208v unit is connected to a 240v supply? Ans: — higher wattage
created will damage heaters or other components
how can the cooking characteristics of equipment be changed by a
low supply voltage? Ans: — slow recovery time, uneven cooking
when is the most opportune time to discover a low or high voltage
problem? Ans: — at equipment startup, before the unit is
energized
can high voltage result in and overheating problem when trying to
control the temp of an oven? Ans: — yes
how many resistances must you have to have a balanced load?
Ans: — 3 or a multiple of 3
what is the formula for calculating the current draw from the
wattage and voltage on a three phase balanced load? Ans: —
amperage = wattage / (voltage X 1.732)
how can you tell if a piece of equipment will be a balanced load or
not? Ans: — must have 3 or a multiple of three loads
© 2025 All rights reserved
CFESA Electrical Questions and Correct
Answers
What do the following prefixes mean? Micro,Kilo,Mega,Milli Ans:
— 1/1,000,000, 1000, 1,000,000, 1/1000
If you know the wattage and voltage, how do you determine the
current? Ans: — Divide the wattage by the voltage
If you know the voltage and current how do you determine the
wattage? Ans: — Multiply voltage times current
If a circuit is supplied with 100 volts and the total resistance of
the circuit is 200 ohms, how much current will the circuit draw?
Ans: — .5 amps
If a piece of equipment is supplied 208 volts and the amp meter
clamped to the hot line reads 20 amps, what is the wattage of the
load? Ans: — 4160 Watts
How much voltage is in one hot line? Ans: — None
What happens to current in a parallel circuit? Ans: — It divides
across resistances
what happens to voltage across the loads in a parallel circuit? Ans:
— stays the same
what happens to the voltage across the loads in a series circuit?
Ans: — it divides across the resistances
what happens to the current in a series circuit? Ans: — It stays the
same everywhere
in a parallel circuit the total resistance of the circuit will always be
less than what resistance? Ans: — the smallest resistance
© 2025 All rights reserved
, 2 | Page
how do you find the total resistance of a series circuit? Ans: — add
the resistances together
how do you find the total resistance of a parallel circuit? Ans: —
1/RT = 1/R1 + 1/R2 + 1/R3 ...
If a circuit is wired parallel, and the supply voltage is 120 volts,
each load must be rated at what voltage? Ans: — 120 volts
if a circuit has two elements wired in series, and each is rated at
120 volts, what voltage must be supplied to the circuit in order for
the elements to heat at full power? Ans: — 240 volts
What is the advantage of using higher voltages? Ans: — Lower
Current and wire size
Is there a negative and positive line in AC power supplies? Ans: —
No
What is the voltage between two hot lines in a 230-volt system?
Ans: — 230V
What is the voltage between two hot lines in a 208-volt system?
Ans: — 208V
What is the voltage between a hot line and a neutral in a 230-volt
single phase supply? Ans: — 115V
What is the voltage between a hot line and a neutral in a 208-volt
single phase supply? Ans: — 120V
What is the accepted maximum voltage difference between the
name plate voltage and the supplied voltage? Ans: — + or - 10%
What is the voltage between any two hot lines of a 230 volt delta
power supply? Ans: — 230V
what is the voltage between a hot line and ground on a 240 volt
delta power supply Ans: — No usable voltage
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what is the voltage between any two hot lines of a 230 volt
grounded delta power supply Ans: — 230V
what is the wild leg? Ans: — leg with higher than 120v to ground
or neutral
what danger is the wild leg? Ans: — high voltage that will damage
120v component in the circuit
what is the voltage between either of the non wild leg hot lines and
neutral in a 230 volt grounded delta system? Ans: — 115v
how do you determine which hot line is the wild leg in a 250 volt
grounded delta power supply? Ans: — the one that does not
measure 120 volts to neutral or ground
what danger is there when replacing a three phase circuit breaker
in a 230 volt grounded delta power supply? Ans: — crossing the
hot lines and supplying the wild leg to the wrong terminal in the
unit.
Why is a "WYE" power supply so versatile Ans: — can get 120v and
208v as well as single and three phase
What is the voltage between any two hot lines in a 208 volt WYE
power supply? Ans: — 208v
What is the voltage between any hot line and neutral or ground in
a 208 volt WYE power supply? Ans: — 120v
What is the voltage from any hot line to ground or neutral, on a
480 volt WYE power supply? Ans: — 277v
if you had a commercial building and you had a three phase
supply to your building how many different incoming power
supplies would you need if the incoming three phase supply was
three phase delta? Ans: — 2
© 2025 All rights reserved
, 4 | Page
if you had a commercial building and you had a three phase
supply to your building, how many different incoming power
supplies would you need if the incoming three phase supply was
three phase grounded delta? Ans: — 1
if you had a commercial building and you had a three phase
supply to your building how many different incoming power
supplies would you need if the incoming three phase supply was
three phase WYE 208v? Ans: — 1
approximately how much will the wattage increase on a 208v piece
of equipment if it is connected to 240v supply? Ans: — 33%
approximately how much will the rated wattage decrease if a 240v
unit is connected to a 208v power supply? Ans: — 25%
what damage could potentially be caused to the supply wiring if
208v unit is connected to a 240v supply? Ans: — higher wattage
created will damage heaters or other components
how can the cooking characteristics of equipment be changed by a
low supply voltage? Ans: — slow recovery time, uneven cooking
when is the most opportune time to discover a low or high voltage
problem? Ans: — at equipment startup, before the unit is
energized
can high voltage result in and overheating problem when trying to
control the temp of an oven? Ans: — yes
how many resistances must you have to have a balanced load?
Ans: — 3 or a multiple of 3
what is the formula for calculating the current draw from the
wattage and voltage on a three phase balanced load? Ans: —
amperage = wattage / (voltage X 1.732)
how can you tell if a piece of equipment will be a balanced load or
not? Ans: — must have 3 or a multiple of three loads
© 2025 All rights reserved
