BPSC AEO Electrical Preliminary Mock Test – Part 1 (Circuits & Network Analysis, Q1–20)
- A series RLC circuit has R = 10 Ω, L = 0.1 H, C = 100 μF, applied voltage 220 V, 50 Hz. The current will be:
a) 2 A
b) 1 A
c) 1.5 A
d) 0.5 A - A 3-phase star-connected load of impedance 10 + j5 Ω is connected to 400 V line voltage. Line current is:
a) 20 A
b) 15 A
c) 10 A
d) 12 A - In a series RLC circuit, resonance occurs at 50 Hz. If L = 0.1 H, C is:
a) 100 μF
b) 50 μF
c) 200 μF
d) 150 μF - Maximum power transfer occurs when load resistance RL =
a) Zero
b) Rsource
c) 2 × Rsource
d) Infinite - A voltage source V = 100 V is applied across a series R-L circuit. If V_R = 60 V, V_L = 80 V, total current I =
a) 1 A
b) 0.5 A
c) 2 A
d) 1.5 A - The phase angle between voltage and current in a purely inductive circuit is:
a) 0°
b) 90°
c) 180°
d) 45° - In a delta-connected load, line voltage = 400 V, phase voltage =
a) 400 V
b) 230 V
c) 346 V
d) 200 V - The RMS value of a sinusoidal current i = 10 sin(314 t) A is:
a) 10 A
b) 7.07 A
c) 5 A
d) 14.14 A - Superposition theorem is applicable to:
a) Linear circuits only
b) Non-linear circuits
c) Both
d) None - Thevenin equivalent of a network is found by:
a) Shorting voltage sources
b) Opening current sources
c) Both a & b
d) Neither - In a parallel resonance, the circuit draws:
a) Maximum current
b) Minimum current
c) Zero current
d) Infinite current - In a single-phase AC circuit, power factor is defined as:
a) Cos φ
b) Sin φ
c) Tan φ
d) None - Voltage across capacitor in steady-state DC is:
a) Zero
b) V
c) Infinite
d) Half of applied - The quality factor (Q) of series resonant circuit is:
a) XL/R
b) R/XL
c) XC/R
d) R/XC - In a mesh analysis problem with 2 meshes, how many independent currents exist?
a) 1
b) 2
c) 3
d) 4 - The time constant of an RL circuit is:
a) L/R
b) R/L
c) RC
d) 1/RC - For DC transient in RC circuit, voltage across capacitor at t = τ is:
a) 0.63 Vmax
b) 0.37 Vmax
c) 0.5 Vmax
d) Vmax - In a three-phase balanced system, line current = phase current for:
a) Star connection
b) Delta connection
c) Both
d) None - For a sinusoidal current, reactive power Q =
a) VI sin φ
b) VI cos φ
c) V^2/R
d) I^2 R - Norton equivalent current is equal to:
a) Open-circuit voltage / Rth
b) Short-circuit current
c) Load current
d) Zero
Part 2 – Electrical Machines (Q21–50)
- The back EMF of a DC motor is given by:
a) E_b = V – I_a R_a
b) E_b = I_a R_a
c) E_b = V + I_a R_a
d) E_b = V / I_a - In a DC shunt motor, if field flux is halved, the speed approximately:
a) Doubles
b) Halves
c) Remains constant
d) Increases slightly - Torque of a DC motor is proportional to:
a) Armature current × flux
b) Voltage × flux
c) Current squared
d) Voltage squared - A DC shunt motor has V = 220 V, R_a = 0.5 Ω, I_a = 10 A. Back EMF E_b is:
a) 215 V
b) 2150 V
c) 215 kV
d) 210 V - Which of the following is a starting method of DC series motor?
a) Full voltage starter
b) Star-delta starter
c) Auto-transformer starter
d) Resistance starter - Armature reaction in DC machines causes:
a) Flux weakening
b) Excessive sparking at brushes
c) Shift of neutral axis
d) All of the above - Equivalent circuit of an induction motor rotor referred to stator is used to:
a) Calculate torque
b) Calculate efficiency
c) Solve current equations
d) All of the above - Slip of a 3-phase induction motor at full load is typically:
a) 0.001–0.01
b) 0.01–0.05
c) 0.05–0.1
d) 0.1–0.2 - A 50 Hz induction motor has rotor frequency of 1.5 Hz. Slip is:
a) 0.03
b) 0.1
c) 0.02
d) 0.05 - Single-phase induction motors are generally started by:
a) Direct online
b) Capacitor start
c) Star-delta starter
d) Autotransformer - EMF generated by alternator depends on:
a) Speed, flux, number of turns
b) Load resistance
c) Power factor
d) Efficiency - Synchronous motor operates at:
a) Speed < synchronous speed
b) Speed = synchronous speed
c) Speed > synchronous speed
d) Variable speed - Reactive power of synchronous motor can be controlled by:
a) Changing excitation
b) Changing load
c) Changing voltage
d) Changing frequency - EMF of a single-phase transformer is proportional to:
a) Frequency × flux × turns
b) Voltage × current
c) Load × resistance
d) Efficiency - A 5 kVA, 220/110 V single-phase transformer, primary current at full load:
a) 22.7 A
b) 45.4 A
c) 20 A
d) 10 A - Open-circuit test on transformer is used to determine:
a) Core loss
b) Copper loss
c) Efficiency
d) Voltage regulation - Short-circuit test on transformer is used to determine:
a) Resistance and leakage reactance
b) Core loss
c) Efficiency
d) Voltage regulation - Auto-transformer reduces:
a) Material cost
b) Copper loss
c) Both a & b
d) Neither - For a Δ-Y transformer, line voltage on Y-side is:
a) Line voltage / √3
b) Line voltage × √3
c) Equal to line voltage on Δ-side
d) None of these - Per-unit system is mainly used for:
a) Simplifying calculations
b) Normalizing quantities
c) Fault analysis
d) All of the above - Torque developed by DC motor is maximum when:
a) Flux is zero
b) Armature current is maximum
c) Both flux and current are optimal
d) Voltage is zero - Speed control of DC shunt motor is commonly done by:
a) Armature voltage control
b) Field flux control
c) Both a & b
d) None - 3-phase induction motor input = 415 V, 20 A, efficiency = 90%. Output power =
a) 7.5 kW
b) 12 kW
c) 11 kW
d) 13 kW - Efficiency of synchronous generator depends on:
a) Load
b) Power factor
c) Copper & core loss
d) All of the above - Equivalent circuit of transformer referred to primary side helps in:
a) Load calculation
b) Regulation calculation
c) Fault calculation
d) All - Alternator excitation affects:
a) Terminal voltage
b) Reactive power
c) Both a & b
d) Efficiency - Synchronous reactance is found from:
a) OC & SC test
b) Load test
c) Efficiency test
d) Insulation test - Synchronous condenser is used for:
a) Power factor correction
b) Voltage regulation
c) Reactive power supply
d) All of the above - Torque-slip characteristic of induction motor shows:
a) Pull-out torque
b) Starting torque
c) Maximum torque
d) All - Stepper motors are used for:
a) Precise angular movement
b) High torque only
c) Power generation
d) Voltage regulation
Part 3 – Power Systems & Protection (Q51–70)
- Transmission line resistance per phase is 0.5 Ω, inductive reactance 1 Ω, sending voltage 220 kV, receiving end 200 kV. The line efficiency is approximately:
a) 90%
b) 80%
c) 85%
d) 95% - For a short transmission line, the shunt capacitance is:
a) Negligible
b) Significant
c) Infinite
d) Zero - Medium transmission lines are represented by:
a) π-model
b) T-model
c) Both a & b
d) None - ABCD parameters of a lossless line:
a) A = D = 1
b) B = Z
c) C = 0
d) All of the above - Voltage regulation of a transmission line is:
a) (Vs – Vr)/Vr × 100%
b) (Vr – Vs)/Vr × 100%
c) (Vs – Vr)/Vs × 100%
d) (Vr – Vs)/Vs × 100% - Efficiency of transmission line is:
a) Pr/Ps × 100%
b) Ps/Pr × 100%
c) (Pr – Pl)/Pr × 100%
d) None of the above - Gauss-Seidel method is used for:
a) Load flow analysis
b) Fault calculation
c) Stability study
d) None - Line-to-ground fault in a 3-phase system involves:
a) Phase A and neutral
b) Two phases only
c) All three phases
d) None - Fault current in a system is maximum for:
a) Symmetrical fault
b) Line-to-ground fault
c) Line-to-line fault
d) Three-phase fault - Protective relays operate on:
a) Current
b) Voltage
c) Both current and voltage
d) Resistance - Overcurrent relay is used for:
a) Transformer protection
b) Line protection
c) Motor protection
d) All of the above - Differential relay protects:
a) Transformer
b) Generator
c) Busbar
d) All of the above - Distance relay operates based on:
a) Impedance
b) Current
c) Voltage
d) Power - The common type of circuit breaker for 400 kV lines is:
a) Air circuit breaker
b) Oil circuit breaker
c) SF6 circuit breaker
d) Vacuum circuit breaker - Fault calculations in power systems are done using:
a) Per-unit system
b) Ohm’s law only
c) Kirchhoff’s voltage law
d) None - Substation bus arrangement mainly includes:
a) Single bus
b) Double bus
c) Ring bus
d) All of the above - Load shedding in power system is used to:
a) Prevent blackout
b) Increase generation
c) Decrease transmission losses
d) None - Per-unit system simplifies:
a) Fault analysis
b) Load flow calculation
c) Transformer calculations
d) All of the above - Transformer protection schemes include:
a) Differential protection
b) Buchholz relay
c) Both a & b
d) Overload relay only - Reactive power compensation in transmission lines is done by:
a) Shunt capacitor
b) Series capacitor
c) Synchronous condenser
d) Both a & c
Part 4 – Electrical Measurements & Instrumentation (Q71–85)
- Moving coil instruments can measure:
a) AC only
b) DC only
c) Both AC and DC
d) None - Torque developed in a moving coil instrument is proportional to:
a) Square of current
b) Current × Flux
c) Voltage only
d) Resistance - A current transformer (CT) is used to:
a) Step up voltage
b) Step down current
c) Step up current
d) Measure frequency - Potential transformer (PT) is used for:
a) Voltage measurement
b) Current measurement
c) Both voltage and current measurement
d) None - The main source of error in moving iron instruments is:
a) Hysteresis and eddy current
b) Friction
c) Temperature variation
d) Voltage fluctuation - Wattmeter in single-phase AC system measures:
a) Active power
b) Reactive power
c) Apparent power
d) None - Energy meter working is based on:
a) Moving iron principle
b) Electromagnetic induction
c) Electrostatic principle
d) Thermoelectric effect - A Q-meter is used to measure:
a) Inductance and Q-factor
b) Resistance only
c) Capacitance only
d) Frequency only - Two-wattmeter method measures power in:
a) Three-phase balanced system
b) Single-phase system
c) DC system
d) None - Oscilloscope is mainly used to measure:
a) Voltage waveform
b) Frequency
c) Phase difference
d) All of the above - Instrument transformers are tested by:
a) Ratio test
b) Polarity test
c) Both a & b
d) Insulation test only - A strain gauge is used to measure:
a) Force or stress
b) Voltage
c) Current
d) Power - Digital multimeter (DMM) can measure:
a) Voltage
b) Current
c) Resistance
d) All of the above - Loading error in instruments occurs due to:
a) High input impedance
b) Low input impedance
c) Perfect insulation
d) None - Bi-metallic thermometer works on:
a) Thermal expansion of two metals
b) Resistance change
c) Thermoelectric effect
d) Radiation
Part 5 – Control Systems & Power Electronics (Q86–100)
- The transfer function of a DC motor relates:
a) Output voltage to input voltage
b) Output torque to input current
c) Output speed to input voltage
d) None of these - In a control system, an open-loop system:
a) Responds without feedback
b) Responds with feedback
c) Is always stable
d) Has infinite gain - Closed-loop system provides:
a) Accuracy and stability
b) Less accuracy
c) No effect on stability
d) Reduced gain only - PID controller includes:
a) Proportional, Integral, Derivative
b) Power, Inductive, Differential
c) Primary, Intermediate, Derivative
d) None - Routh-Hurwitz criterion is used to determine:
a) System stability
b) Frequency response
c) Time constant
d) Step response - State-space representation uses:
a) Input-output variables only
b) State variables and matrices
c) Transfer function only
d) None - Step response of a second-order system is determined by:
a) Damping ratio
b) Natural frequency
c) Both a & b
d) None - Phase margin indicates:
a) Stability
b) Response speed
c) Overshoot
d) None - A thyristor is triggered by:
a) Gate current
b) Anode voltage
c) Cathode voltage
d) None - Single-phase AC voltage controller controls:
a) RMS voltage
b) Frequency
c) Phase angle
d) Power factor - Inverter converts:
a) DC to AC
b) AC to DC
c) AC to AC
d) DC to DC - Chopper is used to:
a) Step down DC voltage
b) Step up DC voltage
c) Both a & b
d) AC voltage control - Buck converter:
a) Steps down voltage
b) Steps up voltage
c) Maintains constant current
d) AC to DC conversion - UPS (Uninterrupted Power Supply) mainly provides:
a) Backup supply
b) Voltage regulation
c) Both a & b
d) Frequency conversion only - SMPS (Switch Mode Power Supply) is preferred because:
a) High efficiency
b) Compact size
c) Regulated output
d) All of the above
| Q.No | Answer | Q.No | Answer | Q.No | Answer | Q.No | Answer |
|---|---|---|---|---|---|---|---|
| 1 | b | 26 | d | 51 | a | 76 | a |
| 2 | c | 27 | d | 52 | a | 77 | b |
| 3 | a | 28 | c | 53 | c | 78 | a |
| 4 | b | 29 | a | 54 | d | 79 | a |
| 5 | a | 30 | b | 55 | a | 80 | d |
| 6 | b | 31 | a | 56 | a | 81 | c |
| 7 | a | 32 | b | 57 | a | 82 | a |
| 8 | b | 33 | a | 58 | a | 83 | d |
| 9 | a | 34 | a | 59 | d | 84 | b |
| 10 | c | 35 | a | 60 | c | 85 | a |
| 11 | b | 36 | a | 61 | d | 86 | c |
| 12 | a | 37 | a | 62 | d | 87 | a |
| 13 | b | 38 | c | 63 | a | 88 | a |
| 14 | a | 39 | a | 64 | c | 89 | a |
| 15 | b | 40 | d | 65 | a | 90 | a |
| 16 | a | 41 | c | 66 | d | 91 | b |
| 17 | a | 42 | c | 67 | a | 92 | c |
| 18 | b | 43 | c | 68 | d | 93 | a |
| 19 | a | 44 | d | 69 | c | 94 | a |
| 20 | b | 45 | d | 70 | d | 95 | a |
| 21 | a | 46 | c | 71 | b | 96 | a |
| 22 | a | 47 | a | 72 | b | 97 | c |
| 23 | a | 48 | d | 73 | b | 98 | a |
| 24 | a | 49 | d | 74 | a | 99 | c |
| 25 | d | 50 | a | 75 | b | 100 | d |
Short Disclaimer:
This mock test is for practice purposes only. Questions are inspired by previous years’ BPSC AEO Electrical exam papers and are meant to help candidates prepare. Answers are provided for self-assessment; actual exam questions may vary.