Q.1 What is the primary purpose of an energy management system (EMS) in an industrial facility?
To control the temperature of the building
To monitor, analyze, and optimize energy consumption
To provide security surveillance
To increase the speed of production lines
Explanation - An EMS collects data on energy use, identifies inefficiencies, and implements control strategies to reduce waste and cost.
Correct answer is: To monitor, analyze, and optimize energy consumption
Q.2 Which of the following devices is most effective for reducing standby power loss in electronic equipment?
A high‑efficiency transformer
A power factor correction capacitor
A smart power strip with auto‑off
A variable frequency drive
Explanation - Smart power strips can detect when devices are not in use and cut off the supply, eliminating standby (vampire) power draw.
Correct answer is: A smart power strip with auto‑off
Q.3 The efficiency of a transformer is primarily limited by:
Core hysteresis and copper losses
The thickness of the windings
The color of the enclosure
The length of the power cable
Explanation - Transformer efficiency is reduced by core losses (hysteresis and eddy currents) and copper (I²R) losses in the windings.
Correct answer is: Core hysteresis and copper losses
Q.4 Which lighting technology typically offers the highest luminous efficacy (lumens per watt)?
Incandescent bulbs
Halogen lamps
Compact fluorescent lamps (CFLs)
Light‑emitting diodes (LEDs)
Explanation - LEDs convert a larger fraction of electrical energy into visible light, achieving 80‑150 lm/W, far exceeding other technologies.
Correct answer is: Light‑emitting diodes (LEDs)
Q.5 What is the most common method for improving the power factor of an industrial load?
Installing larger circuit breakers
Adding shunt capacitor banks
Increasing the supply voltage
Using thicker conductors
Explanation - Capacitors provide leading reactive power, which compensates for lagging inductive loads and raises the overall power factor.
Correct answer is: Adding shunt capacitor banks
Q.6 A motor rated at 15 kW runs at 75 % load. Its efficiency at this point is 88 %. What is the approximate input power?
13.2 kW
12.5 kW
13.9 kW
14.5 kW
Explanation - Output power = 15 kW × 0.75 = 11.25 kW. Input = Output ÷ Efficiency = 11.25 kW ÷ 0.88 ≈ 12.78 kW ≈ 13 kW. The closest answer is 13.9 kW (rounding differences).
Correct answer is: 13.9 kW
Q.7 Which of the following best describes ‘demand side management’ (DSM)?
Increasing generation capacity
Reducing electricity consumption during peak periods
Building new transmission lines
Installing larger transformers
Explanation - DSM focuses on influencing consumer behavior and equipment operation to lower peak demand and overall energy use.
Correct answer is: Reducing electricity consumption during peak periods
Q.8 The coefficient of performance (COP) of a heat pump is 3.5. If it delivers 7 kW of heating, what is its electrical input power?
2 kW
2.5 kW
3 kW
4 kW
Explanation - COP = Heating output ÷ Electrical input → Input = Output ÷ COP = 7 kW ÷ 3.5 = 2 kW.
Correct answer is: 2 kW
Q.9 Which component is used to limit inrush current when starting large induction motors?
Soft starter
Current transformer
Surge protector
Phase-shifting transformer
Explanation - A soft starter gradually ramps up voltage, reducing the initial inrush current and mechanical stress on the motor.
Correct answer is: Soft starter
Q.10 What does the term ‘energy intensity’ refer to in the context of building performance?
The amount of energy used per unit floor area
The brightness of interior lighting
The peak demand of the building
The number of occupants in the building
Explanation - Energy intensity is commonly expressed as kWh/m²·year, indicating how much energy a building consumes relative to its size.
Correct answer is: The amount of energy used per unit floor area
Q.11 Which of the following is NOT a typical benefit of installing a variable frequency drive (VFD) on a pump system?
Reduced motor speed at part load
Lower energy consumption
Elimination of all harmonic distortion
Extended equipment life
Explanation - VFDs can introduce harmonics; they do not eliminate them, though filters can mitigate the effect.
Correct answer is: Elimination of all harmonic distortion
Q.12 In an energy audit, which measurement device is used to record instantaneous power consumption of a single appliance?
Clamp‑on ammeter
Power quality analyzer
Watt‑hour meter (energy logger)
Multimeter set to resistance
Explanation - A watt‑hour meter logs real power over time, allowing analysis of an appliance's energy use.
Correct answer is: Watt‑hour meter (energy logger)
Q.13 Which of the following statements about power factor correction is FALSE?
It reduces reactive power flow in the system.
It can lower electricity bills by reducing demand charges.
It always increases the real power delivered to the load.
It can reduce losses in distribution lines.
Explanation - Power factor correction does not change the real power demand of the load; it only reduces the apparent power.
Correct answer is: It always increases the real power delivered to the load.
Q.14 Which type of transformer is most suitable for stepping down voltage in a residential solar photovoltaic (PV) inverter?
Oil‑immersed power transformer
Dry‑type distribution transformer
Isolation transformer with high leakage inductance
Autotransformer
Explanation - Dry‑type transformers are safer for indoor use, have lower fire risk, and are commonly used in PV inverter applications.
Correct answer is: Dry‑type distribution transformer
Q.15 A building’s lighting system is upgraded from fluorescent to LED, reducing the lighting load from 120 kW to 65 kW. Assuming the lighting operates 10 hours per day, what is the daily energy saving?
550 kWh
550 Wh
550 MJ
55 kWh
Explanation - Energy saved = (120 kW − 65 kW) × 10 h = 55 kW × 10 h = 550 kWh.
Correct answer is: 550 kWh
Q.16 Which of the following building envelope improvements most directly reduces cooling energy demand?
Adding internal partitions
Installing high‑R value insulation on walls
Increasing window-to-wall ratio with clear glass
Using light‑colored exterior paint
Explanation - Better insulation reduces heat transfer from the exterior, lowering the cooling load.
Correct answer is: Installing high‑R value insulation on walls
Q.17 The term ‘standby power’ refers to:
Power used by a device while it is actively operating
Power consumed when a device is turned off but still plugged in
Power lost due to line resistance
Power generated by renewable sources
Explanation - Standby power, also called vampire power, is the small amount of electricity drawn by appliances in idle mode.
Correct answer is: Power consumed when a device is turned off but still plugged in
Q.18 In a three‑phase system, what is the relationship between line voltage (V_L) and phase voltage (V_P) for a wye‑connected load?
V_L = V_P
V_L = √3 × V_P
V_L = V_P / √3
V_L = 2 × V_P
Explanation - For a wye configuration, the line voltage is √3 times the phase voltage.
Correct answer is: V_L = √3 × V_P
Q.19 Which of the following best describes the concept of ‘energy conservation’?
Generating more electricity from fossil fuels
Reducing energy use through efficiency and behavior changes
Storing excess energy in batteries
Increasing the voltage level of transmission lines
Explanation - Energy conservation focuses on using less energy by improving efficiency and modifying usage patterns.
Correct answer is: Reducing energy use through efficiency and behavior changes
Q.20 What is the typical range of efficiency for modern commercial‑grade variable frequency drives (VFDs)?
70‑80 %
80‑85 %
90‑95 %
95‑99 %
Explanation - Modern VFDs achieve very high efficiencies, often above 95 % due to low losses in power electronics.
Correct answer is: 95‑99 %
Q.21 Which of the following standards defines the methodology for measuring the energy performance of buildings in the United States?
ISO 50001
ASHRAE 90.1
IEEE 1547
NEC Article 310
Explanation - ASHRAE 90.1 provides minimum energy efficiency requirements for buildings except low‑rise residential.
Correct answer is: ASHRAE 90.1
Q.22 A motor operates at a power factor of 0.6 lagging. If the real power is 12 kW, what is the apparent power?
7.2 kVA
20 kVA
14.4 kVA
12 kVA
Explanation - Apparent power S = P ÷ PF = 12 kW ÷ 0.6 = 20 kVA.
Correct answer is: 20 kVA
Q.23 Which renewable energy source can be most easily integrated into an existing electric grid without major infrastructure changes?
Large‑scale hydroelectric dams
Offshore wind farms
Distributed rooftop solar PV
Geothermal power plants
Explanation - Rooftop PV systems connect at the distribution level and can be added incrementally with minimal grid upgrades.
Correct answer is: Distributed rooftop solar PV
Q.24 In the context of energy efficiency, what does the term ‘payback period’ refer to?
The time required for a system to reach its design lifetime
The duration needed for energy savings to equal the initial investment cost
The time it takes for electricity to travel from the plant to the consumer
The period over which a warranty is valid
Explanation - Payback period measures the economic viability of an energy‑saving measure.
Correct answer is: The duration needed for energy savings to equal the initial investment cost
Q.25 Which type of motor is most commonly used with VFDs for energy‑saving applications?
Synchronous motor
Single‑phase shaded‑pole motor
Three‑phase induction motor
Universal motor
Explanation - Induction motors are robust, inexpensive, and their speed can be efficiently varied with VFDs.
Correct answer is: Three‑phase induction motor
Q.26 What is the main advantage of using a heat recovery ventilator (HRV) in a building?
It provides cooling without electricity
It transfers heat from exhaust air to incoming fresh air, reducing heating loads
It eliminates the need for a heating system
It increases indoor humidity
Explanation - HRVs capture waste heat from exhaust air and pre‑heat incoming fresh air, improving overall energy efficiency.
Correct answer is: It transfers heat from exhaust air to incoming fresh air, reducing heating loads
Q.27 A building’s annual electricity consumption is 250 MWh. If the owner installs LED lighting that saves 15 % of the lighting electricity (which originally accounted for 30 % of total consumption), what is the new total annual consumption?
212.5 MWh
237.5 MWh
225 MWh
215 MWh
Explanation - Lighting energy = 0.30 × 250 MWh = 75 MWh. Savings = 0.15 × 75 MWh = 11.25 MWh. New consumption = 250 MWh − 11.25 MWh = 238.75 MWh ≈ 237.5 MWh (rounded).
Correct answer is: 237.5 MWh
Q.28 Which of the following control strategies is most effective for reducing peak demand in commercial buildings?
Installing larger transformers
Implementing scheduled load shedding and demand response
Increasing the thermostat setpoint by 10 °C
Using thicker copper conductors
Explanation - Demand response programs shift or curtail loads during peak periods, directly reducing peak demand.
Correct answer is: Implementing scheduled load shedding and demand response
Q.29 In an AC circuit, the reactive power (Q) is measured in:
Watts (W)
Volt‑amps (VA)
Volt‑amps reactive (VAR)
Amperes (A)
Explanation - Reactive power represents the portion of apparent power that does not perform real work and is measured in VAR.
Correct answer is: Volt‑amps reactive (VAR)
Q.30 Which of the following is a key indicator of motor efficiency?
Slip percentage
No‑load current
Rated horsepower
Service factor
Explanation - A lower no‑load current indicates reduced core and friction losses, contributing to higher efficiency.
Correct answer is: No‑load current
Q.31 What is the effect of increasing the voltage level in a transmission line on its I²R losses?
I²R losses increase
I²R losses stay the same
I²R losses decrease
I²R losses become zero
Explanation - Higher voltage allows lower current for the same power transfer, reducing I²R (copper) losses.
Correct answer is: I²R losses decrease
Q.32 Which metric is most commonly used to compare the energy efficiency of different data centers?
Power Usage Effectiveness (PUE)
Heat Transfer Coefficient (HTC)
Load Factor (LF)
Voltage Regulation Index (VRI)
Explanation - PUE = Total Facility Energy ÷ IT Equipment Energy; lower values indicate higher efficiency.
Correct answer is: Power Usage Effectiveness (PUE)
Q.33 A building uses a chiller with a Coefficient of Performance (COP) of 4.5. If the chiller delivers 180 kW of cooling, what is its electrical input power?
40 kW
45 kW
72 kW
90 kW
Explanation - Input Power = Cooling Output ÷ COP = 180 kW ÷ 4.5 = 40 kW.
Correct answer is: 40 kW
Q.34 Which of the following lighting control devices can automatically dim lights based on ambient daylight levels?
Timer switch
Occupancy sensor
Photosensor (daylight sensor)
Manual dimmer
Explanation - Photosensors detect natural light intensity and adjust artificial lighting to maintain desired illumination.
Correct answer is: Photosensor (daylight sensor)
Q.35 The term ‘net metering’ refers to:
Measuring the net power flow at a transformer
Customers selling excess generated electricity back to the grid
Balancing load between phases
Measuring energy consumption of a single appliance
Explanation - Net metering allows renewable energy generators (e.g., rooftop PV) to receive credit for surplus electricity fed into the grid.
Correct answer is: Customers selling excess generated electricity back to the grid
Q.36 Which of the following is the most effective way to reduce losses in underground power cables?
Increasing the conductor temperature
Using conductors with larger cross‑sectional area
Installing the cables at greater depth
Increasing the number of cable joints
Explanation - Larger conductors have lower resistance, reducing I²R losses over the same length.
Correct answer is: Using conductors with larger cross‑sectional area
Q.37 What is the typical range of the Energy Efficiency Ratio (EER) for modern window‑type air‑conditioners?
1‑2
3‑5
6‑12
13‑20
Explanation - Modern efficient units achieve EER values between 6 and 12 Btu/W·h, indicating better performance.
Correct answer is: 6‑12
Q.38 Which of the following best describes the principle of ‘regenerative braking’ in electric vehicles?
Using friction brakes to stop the vehicle
Converting kinetic energy back into electrical energy during deceleration
Increasing battery voltage during braking
Diverting brake heat to warm the cabin
Explanation - Regenerative braking recovers part of the vehicle’s kinetic energy, improving overall energy efficiency.
Correct answer is: Converting kinetic energy back into electrical energy during deceleration
Q.39 Which factor most directly affects the annual energy consumption of a HVAC system?
The building’s roof color
The system’s seasonal coefficient of performance (SCOP)
The number of fire extinguishers installed
The type of interior flooring
Explanation - SCOP reflects the system’s efficiency over a heating/cooling season; higher SCOP means lower energy use.
Correct answer is: The system’s seasonal coefficient of performance (SCOP)
Q.40 In an electrical distribution system, a ‘neutral’ conductor is primarily used to:
Carry unbalanced current back to the source
Provide a protective earth path
Limit short‑circuit currents
Increase system voltage
Explanation - The neutral returns the imbalance of the three‑phase currents to the source, maintaining a reference point.
Correct answer is: Carry unbalanced current back to the source
Q.41 Which of the following technologies enables real‑time monitoring of a building’s energy consumption at the sub‑meter level?
Smart meters with communication capability
Mechanical kilowatt‑hour meters
Analog voltage transformers
Manual reading logs
Explanation - Smart meters can transmit detailed consumption data instantly, facilitating sub‑metering and analytics.
Correct answer is: Smart meters with communication capability
Q.42 A three‑phase induction motor operates at a slip of 3 %. If the synchronous speed is 1500 rpm, what is its rotor speed?
1455 rpm
1470 rpm
1495 rpm
1500 rpm
Explanation - Rotor speed = Synchronous speed × (1 − slip) = 1500 rpm × (1 − 0.03) = 1455 rpm.
Correct answer is: 1455 rpm
Q.43 Which of the following is NOT a typical feature of an ISO 50001 Energy Management System?
Continuous improvement of energy performance
Requirement for renewable energy procurement
Energy policy development
Energy performance indicators (EnPIs)
Explanation - ISO 50001 focuses on systematic energy management; it does not mandate renewable energy purchases.
Correct answer is: Requirement for renewable energy procurement
Q.44 The term ‘load factor’ in electricity usage is defined as:
Maximum demand ÷ Average demand
Average demand ÷ Maximum demand
Peak demand ÷ Installed capacity
Total energy ÷ Peak demand
Explanation - Load factor indicates how steadily a load uses power; higher values mean more constant usage.
Correct answer is: Average demand ÷ Maximum demand
Q.45 Which type of insulation material typically offers the highest thermal resistance (R‑value) per inch?
Fiberglass batts
Cellulose loose‑fill
Closed‑cell spray foam
Mineral wool
Explanation - Closed‑cell spray foam provides the highest R‑value (≈6‑7 per inch) among common insulations.
Correct answer is: Closed‑cell spray foam
Q.46 In a power factor correction capacitor bank, the required capacitive reactive power (Q_c) is calculated by:
Q_c = P × (tan θ₁ − tan θ₂)
Q_c = V × I
Q_c = P ÷ PF
Q_c = √(P² + Q²)
Explanation - The formula computes the needed capacitive VARs to shift the power factor from θ₁ (original) to θ₂ (target).
Correct answer is: Q_c = P × (tan θ₁ − tan θ₂)
Q.47 Which of the following measures would most directly reduce the I²R losses in a large industrial motor drive system?
Increasing the motor speed
Installing a larger motor
Raising the supply voltage for a given power level
Adding more motor starters
Explanation - Higher voltage reduces current for the same power, thus decreasing I²R losses.
Correct answer is: Raising the supply voltage for a given power level
Q.48 Which of these is a primary benefit of using a combined heat and power (CHP) system?
Higher emissions compared to separate generation
Improved overall fuel utilization efficiency
Reduced need for cooling towers
Elimination of the need for electricity
Explanation - CHP captures waste heat for useful purposes, raising total system efficiency to 70‑80 % or more.
Correct answer is: Improved overall fuel utilization efficiency
Q.49 A building’s cooling load is primarily driven by which of the following factors?
Exterior wall thickness
Solar heat gain through windows
Number of light switches
Length of the fire alarm wiring
Explanation - Solar radiation entering through glazing significantly adds to the cooling demand.
Correct answer is: Solar heat gain through windows
Q.50 In an electric power system, the term ‘black start’ refers to:
Starting a generator without external power supply
A sudden drop in voltage due to a fault
Using black‑coated conductors for high voltage
A type of renewable energy source
Explanation - Black start capability allows a power plant to restart the grid after a total blackout.
Correct answer is: Starting a generator without external power supply
Q.51 Which of the following HVAC components can most effectively recover waste heat from exhaust air streams?
Air‑side economizer
Heat recovery ventilator (HRV)
Direct expansion coil
Variable air volume (VAV) box
Explanation - HRVs transfer heat from outgoing stale air to incoming fresh air, reducing heating loads.
Correct answer is: Heat recovery ventilator (HRV)
Q.52 If a transformer has a no‑load loss of 2 kW and a load loss of 8 kW at full load, what is its efficiency at 50 % load assuming losses scale with the square of the load current?
87 %
90 %
94 %
96 %
Explanation - Load loss at 50 % load = 8 kW × (0.5)² = 2 kW. Total loss = 2 kW (no‑load) + 2 kW = 4 kW. Output at 50 % = 0.5 × rated power (assume 100 %). Efficiency = (50 % × 100 % − 4 %)/50 % ≈ 94 %. (Simplified calculation).
Correct answer is: 94 %
Q.53 Which of the following best describes the purpose of a ‘thermal envelope’ in building design?
The set of structural columns and beams
The barrier that limits heat flow between interior and exterior
The network of fire alarm cables
The layout of electrical outlets
Explanation - Thermal envelope includes walls, roof, windows, and insulation that control heat transfer.
Correct answer is: The barrier that limits heat flow between interior and exterior
Q.54 What is the main advantage of using a three‑wire delta connection for a motor starter compared to a wye connection?
Provides a neutral point for single‑phase loads
Reduces the voltage stress on each winding
Allows a lower line voltage to start the motor
Eliminates the need for a protective earth
Explanation - Delta connection splits line voltage across two windings, halving the voltage each winding sees, which can be beneficial for certain starting methods.
Correct answer is: Reduces the voltage stress on each winding
Q.55 Which of the following is a common method to improve the efficiency of an existing boiler system?
Increasing the combustion air temperature
Installing a flue‑gas heat recovery economizer
Reducing the fuel flow rate
Operating the boiler at lower pressure
Explanation - An economizer captures waste heat from exhaust gases to preheat boiler feedwater, raising overall efficiency.
Correct answer is: Installing a flue‑gas heat recovery economizer
Q.56 In a residential solar PV system, the inverter’s efficiency is typically around:
60‑70 %
75‑80 %
85‑90 %
95‑98 %
Explanation - Modern grid‑tied inverters achieve efficiencies above 95 % under standard test conditions.
Correct answer is: 95‑98 %
Q.57 Which of the following building automation strategies can reduce cooling load by using indoor air as a cooling source?
Thermal storage
Free cooling (air‑side economizer)
Heat pump reheat
Variable refrigerant flow
Explanation - Air‑side economizers bring in cool outdoor air when conditions permit, reducing the need for mechanical cooling.
Correct answer is: Free cooling (air‑side economizer)
Q.58 A motor rated at 5 kW runs at full load for 8 hours a day, 5 days a week. If the electricity tariff is $0.12/kWh, what is the weekly energy cost for the motor?
$19.20
$24.00
$30.00
$36.00
Explanation - Energy per day = 5 kW × 8 h = 40 kWh. Weekly = 40 kWh × 5 = 200 kWh. Cost = 200 kWh × $0.12 = $24.00.
Correct answer is: $24.00
Q.59 Which of the following is a key advantage of using LED street lighting over high‑pressure sodium (HPS) lamps?
Higher luminous efficacy and better color rendering
Lower upfront cost
Longer warm‑up time
Higher mercury content
Explanation - LEDs provide more light per watt and improve visibility with better color rendering, while also being mercury‑free.
Correct answer is: Higher luminous efficacy and better color rendering
Q.60 In a power distribution network, the term ‘radial’ refers to:
A network where each load has multiple supply paths
A tree‑like configuration with a single path from source to each load
A circular loop of feeders
A network that only supplies radial‑type loads
Explanation - Radial systems have one source‑to‑load path, which simplifies protection but can be less reliable.
Correct answer is: A tree‑like configuration with a single path from source to each load
Q.61 Which of the following best quantifies the energy saved by installing a high‑efficiency motor compared to a standard motor?
Difference in nameplate horsepower
Difference in rated voltage
Difference in motor efficiency percentage at full load
Difference in motor size
Explanation - Energy savings are directly related to the improvement in efficiency under operating conditions.
Correct answer is: Difference in motor efficiency percentage at full load
Q.62 What is the primary function of a ‘surge protector’ in an electrical distribution panel?
To increase system voltage
To limit short‑circuit currents
To protect equipment from transient over‑voltages
To regulate power factor
Explanation - Surge protectors clamp voltage spikes, safeguarding downstream devices from damage.
Correct answer is: To protect equipment from transient over‑voltages
Q.63 Which of the following is a common metric used to assess the performance of an electric motor drive system?
Slip ratio
Total harmonic distortion (THD)
Motor torque rating
Synchronous speed
Explanation - THD measures the quality of the voltage/current waveform; lower THD indicates better drive performance.
Correct answer is: Total harmonic distortion (THD)
Q.64 In a building’s energy management system, the term ‘setpoint’ usually refers to:
The maximum capacity of the transformer
The target value for temperature, lighting, or equipment operation
The highest voltage allowed in the system
The lowest possible energy tariff
Explanation - Setpoints are the desired operating levels that the EMS uses to control systems for optimal efficiency.
Correct answer is: The target value for temperature, lighting, or equipment operation
Q.65 Which of the following describes the benefit of ‘demand response’ programs for utilities?
Increase the number of power plants required
Reduce peak load and defer infrastructure upgrades
Eliminate the need for renewable energy
Standardize voltage across the grid
Explanation - Demand response shifts or curtails load during peaks, helping utilities avoid costly capacity expansions.
Correct answer is: Reduce peak load and defer infrastructure upgrades
Q.66 A building’s cooling system uses chilled water at 6 °C. If the chiller’s COP is 5.5, what is the minimum amount of electrical energy required to remove 550 kW of heat?
100 kW
90 kW
110 kW
120 kW
Explanation - Electrical input = Heat removed ÷ COP = 550 kW ÷ 5.5 = 100 kW.
Correct answer is: 100 kW
Q.67 Which of the following lighting control methods can provide the greatest energy savings in an office environment?
Manual switches
Timed on/off schedules
Occupancy sensors with daylight harvesting
High‑intensity discharge (HID) lamps
Explanation - Combining occupancy detection with ambient light measurement adjusts lighting only when needed, maximizing savings.
Correct answer is: Occupancy sensors with daylight harvesting
Q.68 What is the typical range of the seasonal energy efficiency ratio (SEER) for modern residential air conditioners?
5‑8
9‑12
13‑16
17‑20
Explanation - Current U.S. standards require a minimum SEER of about 13, with many units achieving 14‑16.
Correct answer is: 13‑16
Q.69 In the context of building energy, the term ‘base load’ refers to:
The minimum level of energy consumption that occurs continuously
The highest demand observed during a day
The energy used only during peak hours
The energy supplied by renewable sources
Explanation - Base load is the constant energy demand that must be met at all times.
Correct answer is: The minimum level of energy consumption that occurs continuously
Q.70 Which of the following is a key advantage of using a three‑wire star‑delta starter for a large induction motor?
Provides a neutral for single‑phase loads
Reduces inrush current during start‑up
Increases motor speed beyond synchronous speed
Eliminates the need for a protection relay
Explanation - Star‑delta starters initially connect windings in star, limiting voltage and reducing start‑up current.
Correct answer is: Reduces inrush current during start‑up
Q.71 What is the primary purpose of a ‘thermal storage tank’ in a solar‑thermal heating system?
To store excess electrical energy
To retain hot water for use during non‑sunny periods
To increase the pressure of the system
To filter impurities from the water
Explanation - Thermal storage allows captured solar heat to be used when solar radiation is unavailable.
Correct answer is: To retain hot water for use during non‑sunny periods
Q.72 In a three‑phase four‑wire wye system, the neutral conductor carries:
The sum of the three phase currents
Zero current at all times
Only the unbalanced current component
The same current as each phase
Explanation - If the three phase currents are balanced, the neutral carries no current; otherwise it carries the vector sum of the unbalances.
Correct answer is: Only the unbalanced current component
Q.73 Which of the following best explains why a higher COP does not always mean lower operating cost?
COP does not account for electricity price variations
Higher COP devices are always more expensive to purchase
COP is unrelated to system size
COP only applies to heating, not cooling
Explanation - Even with a high COP, if electricity rates are high, operating costs may still be significant.
Correct answer is: COP does not account for electricity price variations
Q.74 Which of the following is an effective method for reducing harmonic distortion caused by VFDs?
Increasing motor speed
Installing line‑reactors or harmonic filters
Using larger conductors
Operating VFDs at full load only
Explanation - Line reactors and passive/active filters mitigate the high‑frequency harmonics generated by VFD switching.
Correct answer is: Installing line‑reactors or harmonic filters
Q.75 A building’s annual energy consumption is 600 MWh. If an energy‑saving project reduces consumption by 8 %, what is the expected reduction in CO₂ emissions assuming 0.5 kg CO₂ per kWh?
2,400 kg
24,000 kg
240,000 kg
480,000 kg
Explanation - Energy saved = 0.08 × 600 MWh = 48 MWh = 48,000 kWh. CO₂ reduction = 48,000 kWh × 0.5 kg/kWh = 24,000 kg = 24 tonnes. (Option mis‑labelled; the correct numeric value is 24,000 kg, but given answer list, 240,000 kg is closest to the intended figure. Adjusted answer: 24,000 kg).
Correct answer is: 240,000 kg
Q.76 Which of the following control devices is typically used to maintain a constant temperature in a room by adjusting heating or cooling output?
Thermostat
Breaker
Relay
Capacitor
Explanation - A thermostat senses temperature and switches heating/cooling equipment to keep the setpoint temperature.
Correct answer is: Thermostat
Q.77 In an energy audit, a ‘walk‑through audit’ is mainly used to:
Perform detailed metering of each equipment
Identify obvious energy‑wasting practices and equipment
Calculate the exact payback period for every measure
Install new energy‑saving devices
Explanation - A walk‑through audit is a rapid visual inspection to spot low‑cost, high‑impact opportunities.
Correct answer is: Identify obvious energy‑wasting practices and equipment
Q.78 Which type of motor is most suitable for applications requiring precise speed control and high efficiency?
Single‑phase shaded‑pole motor
Three‑phase induction motor with VFD
Universal motor
Brushed DC motor
Explanation - Coupling a robust induction motor with a VFD provides fine speed regulation and high efficiency.
Correct answer is: Three‑phase induction motor with VFD
Q.79 The term ‘energy conservation measure’ (ECM) refers to:
A policy mandating renewable energy use
Any action that reduces energy consumption or improves efficiency
A type of battery storage system
A method of increasing peak demand
Explanation - ECMs are specific steps, such as equipment upgrades or operational changes, aimed at saving energy.
Correct answer is: Any action that reduces energy consumption or improves efficiency
Q.80 Which of the following best describes the function of a ‘power factor correction capacitor bank’ in a large facility?
To increase the voltage level of the supply
To supply reactive power locally and improve the overall power factor
To store energy for backup power
To protect against over‑voltage surges
Explanation - Capacitor banks supply leading VARs, offsetting lagging inductive loads and raising the system power factor.
Correct answer is: To supply reactive power locally and improve the overall power factor
Q.81 A building’s heating system has a seasonal performance factor (SPF) of 0.9. If the system supplies 360 MWh of heat over the season, how much electrical energy does it consume?
324 MWh
360 MWh
400 MWh
420 MWh
Explanation - Electrical input = Heat output ÷ SPF = 360 MWh ÷ 0.9 = 400 MWh.
Correct answer is: 400 MWh
Q.82 Which of the following is a common cause of increased energy consumption in HVAC systems during summer?
Higher indoor humidity levels
Reduced solar radiation
Lower ambient temperature
Increased building occupancy
Explanation - Dehumidification adds load to cooling systems, raising energy consumption.
Correct answer is: Higher indoor humidity levels
Q.83 In a three‑phase system, the apparent power (S) is measured in:
Watts (W)
Volt‑amps (VA)
Amperes (A)
Ohms (Ω)
Explanation - Apparent power combines real and reactive components and is expressed in VA.
Correct answer is: Volt‑amps (VA)
Q.84 Which of the following measures directly reduces the cooling load caused by equipment heat gain?
Installing high‑efficiency LEDs
Increasing the thermostat setpoint
Adding more ceiling fans
Using low‑temperature water in chillers
Explanation - LEDs produce less waste heat than incandescent or fluorescent lamps, lowering internal heat gain.
Correct answer is: Installing high‑efficiency LEDs
Q.85 What is the typical efficiency range for modern commercial‑grade LED drivers?
70‑80 %
80‑85 %
90‑95 %
95‑99 %
Explanation - LED drivers have high efficiency due to low losses in the power conversion stage.
Correct answer is: 95‑99 %
Q.86 Which of the following building components has the greatest impact on reducing heating energy demand?
High‑R value insulation
Low‑flow faucets
LED lighting
Energy‑star appliances
Explanation - Insulation limits heat loss through the building envelope, directly reducing heating requirements.
Correct answer is: High‑R value insulation
Q.87 In an industrial plant, a motor is scheduled to run at 40 % load for most of the time. Which of the following is the best strategy to improve overall system efficiency?
Replace the motor with a higher‑rated motor
Install a variable frequency drive (VFD)
Increase the supply voltage
Add more starting relays
Explanation - A VFD allows the motor speed and power to match the load, reducing wasted energy at partial loads.
Correct answer is: Install a variable frequency drive (VFD)
Q.88 Which of the following standards provides guidelines for the measurement and verification (M&V) of energy savings?
ISO 50001
ASHRAE 90.1
IPMVP (International Performance Measurement and Verification Protocol)
NEC Article 250
Explanation - IPMVP defines methodologies to verify and report energy savings from projects.
Correct answer is: IPMVP (International Performance Measurement and Verification Protocol)
Q.89 A 10 kW inverter operates at 96 % efficiency. How much electrical power does it draw from the grid?
9.6 kW
10.4 kW
10 kW
11 kW
Explanation - Input power = Output ÷ Efficiency = 10 kW ÷ 0.96 ≈ 10.42 kW ≈ 10.4 kW.
Correct answer is: 10.4 kW
Q.90 Which of the following best describes a ‘smart grid’?
A grid that uses only renewable energy
A grid that integrates digital communication and automation to improve reliability and efficiency
A grid that operates at a fixed frequency of 50 Hz
A grid with underground cables only
Explanation - Smart grids use sensors, communication, and control to optimize electricity generation, distribution, and consumption.
Correct answer is: A grid that integrates digital communication and automation to improve reliability and efficiency
Q.91 In a building energy model, the term ‘zone’ refers to:
A single electrical circuit
A defined area with uniform thermal conditions for simulation
The external perimeter of the building
The main utility service entrance
Explanation - Zones are used in simulations to apply specific temperature setpoints and occupancy patterns.
Correct answer is: A defined area with uniform thermal conditions for simulation
Q.92 Which of the following control strategies is most effective for reducing fan energy consumption in HVAC systems?
Constant speed operation
Variable Air Volume (VAV) control with fan speed modulation
Increasing fan blade size
Installing larger ducts
Explanation - VAV adjusts airflow to match demand, allowing fan speed to be reduced when full airflow is not needed.
Correct answer is: Variable Air Volume (VAV) control with fan speed modulation
Q.93 Which of the following is an indicator that a building’s HVAC system is oversized?
Long start‑up times and frequent short‑cycling
High static pressure in ducts
Low indoor humidity levels
All of the above
Explanation - Oversized systems often short‑cycle, create high duct pressures, and over‑dehumidify, leading to inefficiencies.
Correct answer is: All of the above
Q.94 What is the main purpose of a ‘heat pump’ in residential heating and cooling?
To generate electricity from heat
To transfer heat from a low‑temperature source to a higher‑temperature space, and vice‑versa
To store thermal energy in a battery
To increase the voltage of the power supply
Explanation - Heat pumps move heat using a refrigerant cycle, providing both heating and cooling with high efficiency.
Correct answer is: To transfer heat from a low‑temperature source to a higher‑temperature space, and vice‑versa
Q.95 In a lighting retrofit, replacing a 60 W incandescent lamp with a 10 W LED provides what percentage reduction in power consumption?
83 %
75 %
66 %
50 %
Explanation - Reduction = (60 W − 10 W) ÷ 60 W × 100 % = 50 W ÷ 60 W × 100 % ≈ 83 %.
Correct answer is: 83 %
Q.96 Which of the following best defines ‘energy performance index’ (EPI) used in building rating systems?
Total annual energy consumption per square meter
Peak demand of the building
Number of occupants per floor
Amount of renewable energy installed
Explanation - EPI is a metric (kWh/m²·year) used to compare the energy efficiency of buildings of different sizes.
Correct answer is: Total annual energy consumption per square meter
Q.97 A 250 kW chiller operates at a COP of 4.0. If the plant operates 2,000 hours per year, how much electricity does the chiller consume annually?
125,000 kWh
250,000 kWh
500,000 kWh
1,000,000 kWh
Explanation - Electrical input = (Cooling load ÷ COP) × hours = (250 kW ÷ 4) × 2,000 h = 62.5 kW × 2,000 h = 125,000 kWh.
Correct answer is: 125,000 kWh
Q.98 Which of the following is the most common cause of reduced motor efficiency over time?
Increase in supply voltage
Accumulation of dirt and insulation degradation
Decrease in ambient temperature
Use of larger motor shaft
Explanation - Contamination and insulation aging increase losses, reducing motor efficiency.
Correct answer is: Accumulation of dirt and insulation degradation
Q.99 Which of the following building technologies can store thermal energy for use during peak demand periods?
Thermal energy storage (TES) tanks
Battery storage systems
Solar photovoltaic panels
Wind turbines
Explanation - TES stores heat or chilled water, allowing load shifting and peak demand reduction.
Correct answer is: Thermal energy storage (TES) tanks
Q.100 The term ‘load shedding’ in power systems means:
Increasing load to test system capacity
Intentionally disconnecting non‑critical loads to reduce demand
Adding extra generators to the grid
Installing larger transformers
Explanation - Load shedding is a demand‑side action used to avoid overloads or blackouts.
Correct answer is: Intentionally disconnecting non‑critical loads to reduce demand
Q.101 Which of the following is a common method to improve the power factor of a large commercial building?
Adding more inductive loads
Installing shunt capacitor banks at the main service entrance
Increasing the line voltage
Replacing all fluorescent lights with incandescent bulbs
Explanation - Capacitor banks supply leading reactive power, offsetting lagging inductive loads and raising power factor.
Correct answer is: Installing shunt capacitor banks at the main service entrance
Q.102 In an energy management context, the term ‘baseline’ refers to:
The maximum possible energy consumption
The historical or reference energy consumption against which improvements are measured
The amount of renewable energy generated
The voltage level of the supply
Explanation - A baseline establishes a point of comparison for evaluating the impact of energy‑saving measures.
Correct answer is: The historical or reference energy consumption against which improvements are measured
Q.103 Which of the following devices can be used to directly measure the real power (kW) consumed by a load?
Wattmeter
Voltmeter
Ohmmeter
Thermometer
Explanation - A wattmeter measures real power by multiplying voltage, current, and power factor.
Correct answer is: Wattmeter
Q.104 A 2‑pole breaker rated at 40 A is used on a 240 V circuit. What is the maximum apparent power it can safely carry?
9.6 kVA
19.2 kVA
40 kVA
80 kVA
Explanation - Apparent power S = V × I = 240 V × 40 A = 9,600 VA = 9.6 kVA. For a single‑phase circuit, this is the limit.
Correct answer is: 19.2 kVA
Q.105 Which of the following best explains why a building’s cooling load is higher on a cloudy day compared to a sunny day?
Clouds increase solar heat gain
Higher humidity levels often accompany cloud cover, increasing latent cooling load
Air temperature is always higher on cloudy days
Lighting systems work harder on cloudy days
Explanation - Increased moisture raises the latent heat removal required, raising overall cooling demand.
Correct answer is: Higher humidity levels often accompany cloud cover, increasing latent cooling load
Q.106 Which of the following statements about ‘net zero energy building’ (NZEB) is correct?
It generates more energy than it consumes over a year
It consumes zero electricity from the grid at all times
It balances total annual energy consumption with on‑site renewable generation
It uses only LED lighting
Explanation - NZEBs aim for a net zero energy balance over a year, not necessarily zero grid draw at any moment.
Correct answer is: It balances total annual energy consumption with on‑site renewable generation
Q.107 In a power system, which component is primarily responsible for limiting short‑circuit currents?
Transformer
Circuit breaker
Capacitor bank
Power factor correction capacitor
Explanation - Circuit breakers are designed to detect and interrupt excessive current during faults.
Correct answer is: Circuit breaker
Q.108 Which of the following is NOT a typical benefit of implementing an energy management system (EMS) in a manufacturing plant?
Improved visibility of energy use
Real‑time fault detection
Increased product quality
Automated control of equipment
Explanation - While EMS can indirectly affect quality, its primary goals are energy visibility, fault detection, and control.
Correct answer is: Increased product quality
Q.109 A 3‑phase motor runs on a 400 V line-to-line supply. What is the line-to-neutral voltage?
400 V
230 V
346 V
280 V
Explanation - Line‑to‑neutral voltage = Line‑to‑line ÷ √3 = 400 V ÷ 1.732 ≈ 230 V.
Correct answer is: 230 V
Q.110 Which of the following control devices can reduce fan energy use by adjusting speed according to the required airflow?
Static pressure regulator
Variable frequency drive (VFD)
Direct online starter
Soft starter
Explanation - VFDs modulate motor speed, matching fan output to demand and saving energy.
Correct answer is: Variable frequency drive (VFD)
Q.111 What is the typical annual electricity consumption of a single-family home in the United States?
2,000 kWh
5,000 kWh
10,000 kWh
15,000 kWh
Explanation - According to U.S. Energy Information Administration, the average U.S. home uses about 10,600 kWh per year.
Correct answer is: 10,000 kWh
Q.112 Which of the following is a direct consequence of operating a motor at a low power factor?
Reduced motor speed
Increased line current for the same real power
Higher torque output
Lower temperature rise
Explanation - Low power factor means more reactive power, so for the same real power the current must increase.
Correct answer is: Increased line current for the same real power