Electrical PE Review UPDATED ACTUAL
Exam Questions and CORRECT Answers
Three identical complex single-phase impedance loads are delta connected to make a
complex three-phase load. Assuming balanced conditions, select the answer below that
describes what would happen if the same load was wye connected instead.
(A) The load would draw the same amount of line current.
(B) The load would draw 1.73 times more line current.
(C) The load would draw 1.73 times less line current.
(D) The load would draw 3 times less line current. - CORRECT ANSWER - (D) The load
would draw 3 times less line current.
The wye-connected three-phase load made from three identical complex single-phase loads will
draw 3 times less line current compared to a delta-connected three-phase load made from the
same three identical complex single-phase loads.
Three identical complex single-phase impedance loads are wye connected to make a
complex three-phase load. Assuming balanced conditions, select the answer below that
describes what would happen if the same load was delta connected instead.
(A) The load would draw the same amount of apparent power.
(B) The load would draw 3 times more apparent power.
(C) The load would draw 1.73 times more apparent power.
(D) The load would draw 1.73 times less apparent power. - CORRECT ANSWER - (B)
The load would draw 3 times more apparent power.
We saw from the previous problem that the delta-connected load will draw 3 times more line
current than the wye-connected load.
This will also result in drawing 3 times more apparent power compared to the wye-connected
load with an equal impedance per-phase.
A complex three-phase wye-connected load and a complex three-phase
,delta-connected load both have the same power rating and power factor. Select the
statement below that is true.
(A) Both loads will draw the same amount of line current.
(B) The wye-connected load will draw 3 times more line current compared to the
delta-connected load.
(C) The wye-connected load will draw 3 times less line current compared to the
delta-connected load.
(D) The wye-connected load will draw 1.73 times less line current compared to the
delta-connected load. - CORRECT ANSWER - Answer: (A) Both loads will draw the
same amount of line current.
If both loads have the same power rating and power factor, they will draw the same amount of
line current and power regardless of if one is wye connected and the other is delta connected.
For a balanced and positive (ABC) sequence system, select the statement below that is
true for a wye connection.
(A) The phase voltage and line voltage are in phase.
(B) The phase voltage leads the line voltage by 30 degrees.
(C) The phase voltage lags the line voltage by 30 degrees.
(D) The displacement angle between the phase voltage and line voltage depends on the
load. - CORRECT ANSWER - Answer: (C) The phase voltage lags the line voltage by 30
degrees.
For a balanced and positive (ABC) sequence system, the phase voltage always lags the line
voltage by 30 degrees.
For a balanced and positive (ABC) sequence system, select the statement below that is
true for a delta connection.
(A) The phase current and line current are in phase.
(B) The phase current leads the line current by 30 degrees.
(C) The phase current lags the line current by 30 degrees.
,(D) The displacement angle between the phase current and line current depends on the
load. - CORRECT ANSWER - Answer: (B) The phase current leads the line current by 30
degrees.
For a balanced and positive (ABC) sequence system, the phase current always leads the line
current by 30 degrees.
For a balanced and negative (ACB) sequence system, select the statement below that is
true for a wye connection.
(A) The phase voltage and line voltage are in phase.
(B) The phase voltage leads the line voltage by 30 degrees.
(C) The phase voltage lags the line voltage by 30 degrees.
(D) The displacement angle between the phase voltage and line voltage depends on the
load. - CORRECT ANSWER - Answer: (B) The phase voltage leads the line voltage by 30
degrees.
For a balanced and negative (ACB) sequence system, the phase voltage always leads the line
voltage by 30 degrees.
For a balanced and negative (ACB) sequence system, select the statement below that is
true for a delta connection.
(A) The phase current and line current are in phase.
(B) The phase current leads the line current by 30 degrees.
(C) The phase current lags the line current by 30 degrees.
(D) The displacement angle between the phase current and line current depends on the
load. - CORRECT ANSWER - Answer: (C) The phase current lags the line current by 30
degrees.
For a balanced and negative (ACB) sequence system, the phase current always lags the line
current by 30 degrees.
Select the statement below that is true in order to accurately measure the real power
, drawn by an unbalanced three-phase system.
(A) Wattmeters can only be used to accurately measure the power of a balanced
three-phase system.
(B) The minimum number of wattmeters required is three.
(C) The minimum number of wattmeters required is two.
(D) The minimum number of wattmeters required is one. - CORRECT ANSWER -
Answer: (C) The minimum number of wattmeters is two.
Most power systems in real life are unbalanced. Balanced or not, the minimum number of
wattmeters required to measure the power drawn by a three-phase system is two, using what is
known as the two-wattmeter method.
Select the relationship below that determines when a transient RC circuit will reach
steady state conditions.
(A) The coefficient 5 multiplied by the circuit resistance (ohms) and capacitance (farads).
(B) The coefficient 5 multiplied by the circuit resistance (ohms) divided by capacitance
(farads).
(C) The coefficient 5 multiplied by the capacitance (farads) divided by the circuit
resistance (ohms).
(D) There is not enough information given to determine when the circuit will reach steady
state conditions. - CORRECT ANSWER - Answer: (A) The coefficient 5 multiplied by the
circuit resistance (ohms) and capacitance
(farads).
A transient RC circuit reaches steady state conditions after approximately 5 time constants (5τ).
The time constant of an RC circuit is defined as the circuit resistance (ohms) multiplied by the
capacitance (farads). Putting it all together, 5 time constants for an RC circuit is 5RC.
Select the relationship below that determines when a transient RL circuit will reach
steady state conditions.
(A) The coefficient 5 multiplied by the circuit resistance (ohms) and inductance (henrys).
Exam Questions and CORRECT Answers
Three identical complex single-phase impedance loads are delta connected to make a
complex three-phase load. Assuming balanced conditions, select the answer below that
describes what would happen if the same load was wye connected instead.
(A) The load would draw the same amount of line current.
(B) The load would draw 1.73 times more line current.
(C) The load would draw 1.73 times less line current.
(D) The load would draw 3 times less line current. - CORRECT ANSWER - (D) The load
would draw 3 times less line current.
The wye-connected three-phase load made from three identical complex single-phase loads will
draw 3 times less line current compared to a delta-connected three-phase load made from the
same three identical complex single-phase loads.
Three identical complex single-phase impedance loads are wye connected to make a
complex three-phase load. Assuming balanced conditions, select the answer below that
describes what would happen if the same load was delta connected instead.
(A) The load would draw the same amount of apparent power.
(B) The load would draw 3 times more apparent power.
(C) The load would draw 1.73 times more apparent power.
(D) The load would draw 1.73 times less apparent power. - CORRECT ANSWER - (B)
The load would draw 3 times more apparent power.
We saw from the previous problem that the delta-connected load will draw 3 times more line
current than the wye-connected load.
This will also result in drawing 3 times more apparent power compared to the wye-connected
load with an equal impedance per-phase.
A complex three-phase wye-connected load and a complex three-phase
,delta-connected load both have the same power rating and power factor. Select the
statement below that is true.
(A) Both loads will draw the same amount of line current.
(B) The wye-connected load will draw 3 times more line current compared to the
delta-connected load.
(C) The wye-connected load will draw 3 times less line current compared to the
delta-connected load.
(D) The wye-connected load will draw 1.73 times less line current compared to the
delta-connected load. - CORRECT ANSWER - Answer: (A) Both loads will draw the
same amount of line current.
If both loads have the same power rating and power factor, they will draw the same amount of
line current and power regardless of if one is wye connected and the other is delta connected.
For a balanced and positive (ABC) sequence system, select the statement below that is
true for a wye connection.
(A) The phase voltage and line voltage are in phase.
(B) The phase voltage leads the line voltage by 30 degrees.
(C) The phase voltage lags the line voltage by 30 degrees.
(D) The displacement angle between the phase voltage and line voltage depends on the
load. - CORRECT ANSWER - Answer: (C) The phase voltage lags the line voltage by 30
degrees.
For a balanced and positive (ABC) sequence system, the phase voltage always lags the line
voltage by 30 degrees.
For a balanced and positive (ABC) sequence system, select the statement below that is
true for a delta connection.
(A) The phase current and line current are in phase.
(B) The phase current leads the line current by 30 degrees.
(C) The phase current lags the line current by 30 degrees.
,(D) The displacement angle between the phase current and line current depends on the
load. - CORRECT ANSWER - Answer: (B) The phase current leads the line current by 30
degrees.
For a balanced and positive (ABC) sequence system, the phase current always leads the line
current by 30 degrees.
For a balanced and negative (ACB) sequence system, select the statement below that is
true for a wye connection.
(A) The phase voltage and line voltage are in phase.
(B) The phase voltage leads the line voltage by 30 degrees.
(C) The phase voltage lags the line voltage by 30 degrees.
(D) The displacement angle between the phase voltage and line voltage depends on the
load. - CORRECT ANSWER - Answer: (B) The phase voltage leads the line voltage by 30
degrees.
For a balanced and negative (ACB) sequence system, the phase voltage always leads the line
voltage by 30 degrees.
For a balanced and negative (ACB) sequence system, select the statement below that is
true for a delta connection.
(A) The phase current and line current are in phase.
(B) The phase current leads the line current by 30 degrees.
(C) The phase current lags the line current by 30 degrees.
(D) The displacement angle between the phase current and line current depends on the
load. - CORRECT ANSWER - Answer: (C) The phase current lags the line current by 30
degrees.
For a balanced and negative (ACB) sequence system, the phase current always lags the line
current by 30 degrees.
Select the statement below that is true in order to accurately measure the real power
, drawn by an unbalanced three-phase system.
(A) Wattmeters can only be used to accurately measure the power of a balanced
three-phase system.
(B) The minimum number of wattmeters required is three.
(C) The minimum number of wattmeters required is two.
(D) The minimum number of wattmeters required is one. - CORRECT ANSWER -
Answer: (C) The minimum number of wattmeters is two.
Most power systems in real life are unbalanced. Balanced or not, the minimum number of
wattmeters required to measure the power drawn by a three-phase system is two, using what is
known as the two-wattmeter method.
Select the relationship below that determines when a transient RC circuit will reach
steady state conditions.
(A) The coefficient 5 multiplied by the circuit resistance (ohms) and capacitance (farads).
(B) The coefficient 5 multiplied by the circuit resistance (ohms) divided by capacitance
(farads).
(C) The coefficient 5 multiplied by the capacitance (farads) divided by the circuit
resistance (ohms).
(D) There is not enough information given to determine when the circuit will reach steady
state conditions. - CORRECT ANSWER - Answer: (A) The coefficient 5 multiplied by the
circuit resistance (ohms) and capacitance
(farads).
A transient RC circuit reaches steady state conditions after approximately 5 time constants (5τ).
The time constant of an RC circuit is defined as the circuit resistance (ohms) multiplied by the
capacitance (farads). Putting it all together, 5 time constants for an RC circuit is 5RC.
Select the relationship below that determines when a transient RL circuit will reach
steady state conditions.
(A) The coefficient 5 multiplied by the circuit resistance (ohms) and inductance (henrys).
