Electrical Engineering and Circuit Analysis
Practice Exam questions and correct
answers– Updated 2026 (Graded A+) instant
download pdf
Subject: Electrical Engineering Principles
Subtopic: Circuit Analysis and Network Theorems
Question 1: A series RLC circuit is connected to an AC voltage source with an angular frequency
$\omega$. If the circuit is operating at a frequency where the inductive reactance ($X_L$) is
significantly greater than the capacitive reactance ($X_C$), what is the phase relationship
between the source voltage and the current?
A) The current lags the voltage by $90^\circ$.
B) The current leads the voltage by some angle $\phi$ between $0^\circ$ and $90^\circ$.
C) The voltage leads the current by some angle $\phi$ between $0^\circ$ and $90^\circ$.
D) The voltage and current are in phase.
Correct Answer: C - The voltage leads the current by some angle $\phi$ between $0^\circ$
and $90^\circ$.
Rationale: In an RLC series circuit, the total impedance is $Z = R + j(X_L - X_C)$. If $X_L >
X_C$, the reactive component is inductive, meaning the total impedance has a positive phase
angle. In a circuit where impedance is inductive, the voltage across the circuit leads the current
flowing through it. Option A would only be true for a pure inductor, and Option B describes a
capacitive circuit.
Question 2: In a balanced three-phase Wye-Wye ($Y-Y$) system, if the line voltage is
$415\text{ V}$, what is the phase voltage?
A) $415\text{ V}$
B) $240\text{ V}$
C) $719\text{ V}$
D) $207.5\text{ V}$
,Correct Answer: B - 240 V
Rationale: In a Wye-connected system, the relationship between line voltage ($V_L$) and phase
voltage ($V_P$) is defined by the formula $V_L = \sqrt{3} \times V_P$. Therefore, $V_P = V_L
/ \sqrt{3}$. Given $V_L = 415\text{ V}$, $.732 \approx 239.6\text{ V}$, which rounds to
$240\text{ V}$.
Question 3: For the circuit shown below, apply Thevenin’s Theorem to determine the Thevenin
equivalent resistance ($R_{th}$) looking into terminals $A$ and $B$. Assume a $10\text{ V}$
source in series with a $5\text{ }\Omega$ resistor, which is in parallel with a $20\text{
}\Omega$ resistor.
A) $4\text{ }\Omega$
B) $5\text{ }\Omega$
C) $25\text{ }\Omega$
D) $20\text{ }\Omega$
Correct Answer: A - 4 $\Omega$
Rationale: To find the Thevenin resistance ($R_{th}$), all independent voltage sources must be
deactivated (short-circuited). With the $10\text{ V}$ source shorted, the $5\text{ }\Omega$ and
$20\text{ }\Omega$ resistors are in parallel. The equivalent resistance is $(5 \times 20) / (5 +
20) = = 4\text{ }\Omega$.
Question 4: An ideal transformer has a turns ratio of $N_1:N_2 = 10:1$. If a $100\text{
}\Omega$ load is connected to the secondary side, what is the reflected impedance seen from the
primary side?
A) $1\text{ }\Omega$
B) $10\text{ }\Omega$
C) $1,000\text{ }\Omega$
D) $10,000\text{ }\Omega$
Correct Answer: D - 10,000 $\Omega$
Rationale: The reflected impedance ($Z_{reflected}$) is calculated using the square of the turns
ratio ($a = N_1/N_2$): $Z_{reflected} = a^2 \times Z_{load}$. Here, $a = 10/1 = 10$. Thus,
$10^2 \times 100\text{ }\Omega = 100 \times 100 = 10,000\text{ }\Omega$.
,Question 5: A DC motor is operating under a steady state. If the field flux is suddenly reduced
while the armature voltage remains constant, how will the motor speed react?
A) The speed will decrease.
B) The speed will increase.
C) The speed will remain constant.
D) The motor will stall immediately.
Correct Answer: B - The speed will increase.
Rationale: The speed of a DC motor is inversely proportional to the magnetic flux ($\phi$)
according to the equation $N \propto V_a / \phi$. If the flux ($\phi$) decreases, the denominator
becomes smaller, leading to an increase in the motor's rotational speed. This is a characteristic
danger in shunt-wound DC motors if the field circuit is opened.
Subtopic: Power Systems and Electrical Machines
Question 6: In a power system, what is the primary purpose of a shunt capacitor bank?
A) To increase the active power demand of the load.
B) To improve the power factor by providing reactive power compensation.
C) To step down the voltage for residential use.
D) To protect the system against lightning surges.
Correct Answer: B - To improve the power factor by providing reactive power
compensation.
Rationale: Inductive loads (like motors) consume reactive power, leading to a lagging power
factor. Shunt capacitors provide leading reactive power to neutralize the inductive demand,
thereby raising the power factor toward unity. This reduces line losses and improves voltage
regulation.
Question 7: A synchronous generator is connected to an infinite bus. If the excitation is increased
(over-excitation), what happens to the reactive power flow?
A) The generator absorbs reactive power from the bus.
B) The generator supplies reactive power to the bus.
C) The reactive power flow remains unchanged.
, D) The generator stops supplying active power.
Correct Answer: B - The generator supplies reactive power to the bus.
Rationale: An over-excited synchronous generator acts like a source of reactive power (similar
to a capacitor). Increasing the field current increases the internal EMF, forcing reactive current
to flow from the generator into the infinite bus.
Question 8: Which type of fault is considered the most common in power transmission lines?
A) Three-phase symmetrical fault.
B) Line-to-line fault.
C) Single line-to-ground fault.
D) Double line-to-ground fault.
Correct Answer: C - Single line-to-ground fault.
Rationale: Statistical analysis of power system operations indicates that the vast majority
(approximately 70-80%) of transmission line faults are single line-to-ground faults, often caused
by lightning strikes, tree branches, or insulation failure.
Question 9: What is the primary function of an autotransformer compared to a conventional two-
winding transformer?
A) To provide electrical isolation between input and output.
B) To achieve voltage transformation using a single shared winding, reducing cost and size.
C) To increase the frequency of the AC signal.
D) To convert AC power to DC power.
Correct Answer: B - To achieve voltage transformation using a single shared winding,
reducing cost and size.
Rationale: Autotransformers use a common winding section for both primary and secondary
circuits. This configuration is more efficient and compact than two-winding transformers but
does not provide the electrical isolation (galvanic isolation) that two-winding transformers offer.
Question 10: In a power system, what is the effect of increasing the transmission voltage on the
line losses ($I^2R$ losses)?
A) Losses increase significantly.
Practice Exam questions and correct
answers– Updated 2026 (Graded A+) instant
download pdf
Subject: Electrical Engineering Principles
Subtopic: Circuit Analysis and Network Theorems
Question 1: A series RLC circuit is connected to an AC voltage source with an angular frequency
$\omega$. If the circuit is operating at a frequency where the inductive reactance ($X_L$) is
significantly greater than the capacitive reactance ($X_C$), what is the phase relationship
between the source voltage and the current?
A) The current lags the voltage by $90^\circ$.
B) The current leads the voltage by some angle $\phi$ between $0^\circ$ and $90^\circ$.
C) The voltage leads the current by some angle $\phi$ between $0^\circ$ and $90^\circ$.
D) The voltage and current are in phase.
Correct Answer: C - The voltage leads the current by some angle $\phi$ between $0^\circ$
and $90^\circ$.
Rationale: In an RLC series circuit, the total impedance is $Z = R + j(X_L - X_C)$. If $X_L >
X_C$, the reactive component is inductive, meaning the total impedance has a positive phase
angle. In a circuit where impedance is inductive, the voltage across the circuit leads the current
flowing through it. Option A would only be true for a pure inductor, and Option B describes a
capacitive circuit.
Question 2: In a balanced three-phase Wye-Wye ($Y-Y$) system, if the line voltage is
$415\text{ V}$, what is the phase voltage?
A) $415\text{ V}$
B) $240\text{ V}$
C) $719\text{ V}$
D) $207.5\text{ V}$
,Correct Answer: B - 240 V
Rationale: In a Wye-connected system, the relationship between line voltage ($V_L$) and phase
voltage ($V_P$) is defined by the formula $V_L = \sqrt{3} \times V_P$. Therefore, $V_P = V_L
/ \sqrt{3}$. Given $V_L = 415\text{ V}$, $.732 \approx 239.6\text{ V}$, which rounds to
$240\text{ V}$.
Question 3: For the circuit shown below, apply Thevenin’s Theorem to determine the Thevenin
equivalent resistance ($R_{th}$) looking into terminals $A$ and $B$. Assume a $10\text{ V}$
source in series with a $5\text{ }\Omega$ resistor, which is in parallel with a $20\text{
}\Omega$ resistor.
A) $4\text{ }\Omega$
B) $5\text{ }\Omega$
C) $25\text{ }\Omega$
D) $20\text{ }\Omega$
Correct Answer: A - 4 $\Omega$
Rationale: To find the Thevenin resistance ($R_{th}$), all independent voltage sources must be
deactivated (short-circuited). With the $10\text{ V}$ source shorted, the $5\text{ }\Omega$ and
$20\text{ }\Omega$ resistors are in parallel. The equivalent resistance is $(5 \times 20) / (5 +
20) = = 4\text{ }\Omega$.
Question 4: An ideal transformer has a turns ratio of $N_1:N_2 = 10:1$. If a $100\text{
}\Omega$ load is connected to the secondary side, what is the reflected impedance seen from the
primary side?
A) $1\text{ }\Omega$
B) $10\text{ }\Omega$
C) $1,000\text{ }\Omega$
D) $10,000\text{ }\Omega$
Correct Answer: D - 10,000 $\Omega$
Rationale: The reflected impedance ($Z_{reflected}$) is calculated using the square of the turns
ratio ($a = N_1/N_2$): $Z_{reflected} = a^2 \times Z_{load}$. Here, $a = 10/1 = 10$. Thus,
$10^2 \times 100\text{ }\Omega = 100 \times 100 = 10,000\text{ }\Omega$.
,Question 5: A DC motor is operating under a steady state. If the field flux is suddenly reduced
while the armature voltage remains constant, how will the motor speed react?
A) The speed will decrease.
B) The speed will increase.
C) The speed will remain constant.
D) The motor will stall immediately.
Correct Answer: B - The speed will increase.
Rationale: The speed of a DC motor is inversely proportional to the magnetic flux ($\phi$)
according to the equation $N \propto V_a / \phi$. If the flux ($\phi$) decreases, the denominator
becomes smaller, leading to an increase in the motor's rotational speed. This is a characteristic
danger in shunt-wound DC motors if the field circuit is opened.
Subtopic: Power Systems and Electrical Machines
Question 6: In a power system, what is the primary purpose of a shunt capacitor bank?
A) To increase the active power demand of the load.
B) To improve the power factor by providing reactive power compensation.
C) To step down the voltage for residential use.
D) To protect the system against lightning surges.
Correct Answer: B - To improve the power factor by providing reactive power
compensation.
Rationale: Inductive loads (like motors) consume reactive power, leading to a lagging power
factor. Shunt capacitors provide leading reactive power to neutralize the inductive demand,
thereby raising the power factor toward unity. This reduces line losses and improves voltage
regulation.
Question 7: A synchronous generator is connected to an infinite bus. If the excitation is increased
(over-excitation), what happens to the reactive power flow?
A) The generator absorbs reactive power from the bus.
B) The generator supplies reactive power to the bus.
C) The reactive power flow remains unchanged.
, D) The generator stops supplying active power.
Correct Answer: B - The generator supplies reactive power to the bus.
Rationale: An over-excited synchronous generator acts like a source of reactive power (similar
to a capacitor). Increasing the field current increases the internal EMF, forcing reactive current
to flow from the generator into the infinite bus.
Question 8: Which type of fault is considered the most common in power transmission lines?
A) Three-phase symmetrical fault.
B) Line-to-line fault.
C) Single line-to-ground fault.
D) Double line-to-ground fault.
Correct Answer: C - Single line-to-ground fault.
Rationale: Statistical analysis of power system operations indicates that the vast majority
(approximately 70-80%) of transmission line faults are single line-to-ground faults, often caused
by lightning strikes, tree branches, or insulation failure.
Question 9: What is the primary function of an autotransformer compared to a conventional two-
winding transformer?
A) To provide electrical isolation between input and output.
B) To achieve voltage transformation using a single shared winding, reducing cost and size.
C) To increase the frequency of the AC signal.
D) To convert AC power to DC power.
Correct Answer: B - To achieve voltage transformation using a single shared winding,
reducing cost and size.
Rationale: Autotransformers use a common winding section for both primary and secondary
circuits. This configuration is more efficient and compact than two-winding transformers but
does not provide the electrical isolation (galvanic isolation) that two-winding transformers offer.
Question 10: In a power system, what is the effect of increasing the transmission voltage on the
line losses ($I^2R$ losses)?
A) Losses increase significantly.
