CITY & GUILDS 2365 UNIT 614
ADVANCED ELECTRICAL SCIENCE
EXAM STUDY GUIDE | QUESTIONS AND
ANSWERS |2026/2027 UPDATE | JUST
RELEASED
1. In a series RLC circuit, at the resonant frequency, the circuit impedance is at its:
A. Minimum value and purely resistive
B. Maximum value and purely inductive
C. Minimum value and purely capacitive
D. Maximum value and purely resistive
Answer: A
Conceptual Explanation: At resonance in a series circuit, inductive reactance (XL) and
capacitive reactance (XC) cancel each other out (XL=XC). The total impedance Z equals the
resistance R, which is its minimum possible value.
2. A star-connected three-phase alternator has a phase voltage of 230V. What is the line
voltage?
A. 230V
B. 460V
,C. 690V
D. 398V
Answer: D
Conceptual Explanation: In a star connection, Line Voltage (VL) = sqrt(3) * Phase Voltage
(VP). Therefore, 230 * 1.732 = 398.36V.
3. Which of the following is the correct formula to calculate the synchronous speed (Ns) of an
AC induction motor?
A. Ns = (f * 120) / P
B. Ns = (P * 120) / f
C. Ns = (f * 60) / P
D. Ns = f / (P * 60)
Answer: A
Conceptual Explanation: Synchronous speed is calculated using the formula Ns = (120 *
frequency) / number of poles.
4. A 400V, three-phase delta-connected motor has a line current of 30A. What is the phase
current?
A. 30A
B. 51.96A
C. 17.32A
, D. 10A
Answer: C
Conceptual Explanation: In a delta connection, IL = sqrt(3) * IP. Therefore, IP = IL /
sqrt(3). .732 = 17.32A.
5. Which component of a DC machine is responsible for converting the AC induced in the
armature to DC at the terminals?
A. The slip rings
B. The commutator
C. The brushes
D. The field poles
Answer: B
Conceptual Explanation: The commutator acts as a mechanical rectifier, reversing the
connections to the external circuit as the armature rotates to maintain a DC output.
6. The ‘Q’ factor (Quality factor) of a series resonant circuit is a measure of its:
A. Power consumption
B. Insulation resistance
C. Current capacity
D. Selectivity and voltage magnification
ADVANCED ELECTRICAL SCIENCE
EXAM STUDY GUIDE | QUESTIONS AND
ANSWERS |2026/2027 UPDATE | JUST
RELEASED
1. In a series RLC circuit, at the resonant frequency, the circuit impedance is at its:
A. Minimum value and purely resistive
B. Maximum value and purely inductive
C. Minimum value and purely capacitive
D. Maximum value and purely resistive
Answer: A
Conceptual Explanation: At resonance in a series circuit, inductive reactance (XL) and
capacitive reactance (XC) cancel each other out (XL=XC). The total impedance Z equals the
resistance R, which is its minimum possible value.
2. A star-connected three-phase alternator has a phase voltage of 230V. What is the line
voltage?
A. 230V
B. 460V
,C. 690V
D. 398V
Answer: D
Conceptual Explanation: In a star connection, Line Voltage (VL) = sqrt(3) * Phase Voltage
(VP). Therefore, 230 * 1.732 = 398.36V.
3. Which of the following is the correct formula to calculate the synchronous speed (Ns) of an
AC induction motor?
A. Ns = (f * 120) / P
B. Ns = (P * 120) / f
C. Ns = (f * 60) / P
D. Ns = f / (P * 60)
Answer: A
Conceptual Explanation: Synchronous speed is calculated using the formula Ns = (120 *
frequency) / number of poles.
4. A 400V, three-phase delta-connected motor has a line current of 30A. What is the phase
current?
A. 30A
B. 51.96A
C. 17.32A
, D. 10A
Answer: C
Conceptual Explanation: In a delta connection, IL = sqrt(3) * IP. Therefore, IP = IL /
sqrt(3). .732 = 17.32A.
5. Which component of a DC machine is responsible for converting the AC induced in the
armature to DC at the terminals?
A. The slip rings
B. The commutator
C. The brushes
D. The field poles
Answer: B
Conceptual Explanation: The commutator acts as a mechanical rectifier, reversing the
connections to the external circuit as the armature rotates to maintain a DC output.
6. The ‘Q’ factor (Quality factor) of a series resonant circuit is a measure of its:
A. Power consumption
B. Insulation resistance
C. Current capacity
D. Selectivity and voltage magnification
