Q1. Expand IOT

A. Internet of things B. Internla C. things D. Net

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Not required

Q2. The primary purpose of the Internet of Things (IoT) is to:

A. connect physical objects so they can sense, communicate and act B. replace every computer with a smartphone C. provide only high-speed internet access D. store all data without any sensing

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: IoT connects physical objects with sensing, processing and communication so that data can be collected and useful actions can be performed.

Q3. Which IoT component primarily converts a physical quantity into an electrical signal?

A. Actuator B. Sensor/transducer C. Router D. Database

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A sensor or transducer detects a physical quantity such as temperature or pressure and produces a corresponding electrical signal.

Q4. Which characteristic is most closely associated with IoT?

A. Isolated operation B. No data exchange C. Connectivity of physical objects D. Manual-only control

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Connectivity is fundamental to IoT because devices exchange data with gateways, networks, cloud services or other devices.

Q5. In a typical IoT system, the sensing layer is mainly responsible for:

A. billing the user B. writing web pages C. printing reports D. collecting physical-world data

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: The sensing/perception layer interfaces with the physical world through sensors and transducers.

Q6. Which layer commonly provides IP networking and data transport in an IoT architecture?

A. Network/communication layer B. Perception layer C. Actuator layer D. Mechanical layer

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: The network layer carries sensor data between edge devices, gateways and processing/cloud systems using communication technologies.

Q7. An actuator in an IoT system is used to:

A. measure temperature B. convert a control signal into physical action C. store a database D. assign an IP address

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: An actuator converts an electrical/control command into a physical action, such as opening a valve or switching a motor.

Q8. Which device is commonly used to measure temperature electronically?

A. Relay coil only B. LED C. Thermistor D. Fuse

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: A thermistor changes resistance with temperature and is widely used for temperature sensing.

Q9. A thermocouple works primarily on the:

A. Hall effect B. Photoelectric effect C. Piezoelectric effect D. Seebeck effect

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: A thermocouple generates a thermoelectric voltage due to a temperature difference between its junctions, known as the Seebeck effect.

Q10. A piezoelectric transducer is particularly suitable for measuring:

A. dynamic force or vibration B. static DC resistance only C. digital memory D. network bandwidth

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Piezoelectric materials generate charge when mechanically stressed, making them useful for vibration and dynamic force measurements.

Q11. Which is an example of an active transducer?

A. Potentiometer B. Thermocouple C. Strain gauge requiring excitation D. RTD requiring excitation

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A thermocouple is self-generating: its temperature difference produces a thermoelectric voltage without an external excitation supply.

Q12. Arduino Uno is commonly based on which microcontroller?

A. ESP32-WROOM only B. 8051 only C. ATmega328P D. ARM Cortex-A72

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: The classic Arduino Uno R3 uses the ATmega328P 8-bit AVR microcontroller.

Q13. Which Arduino function is normally executed repeatedly after setup()?

A. mainLoopOnly() B. repeat() C. runOnce() D. loop()

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Arduino sketches normally contain setup(), which runs once, and loop(), which executes repeatedly.

Q14. Which Arduino function configures a pin as INPUT or OUTPUT?

A. pinMode() B. digitalRead() C. analogRead() D. Serial.print()

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: pinMode(pin, mode) configures a digital pin for INPUT, OUTPUT, or related modes.

Q15. Which Arduino function reads the logic state of a digital input?

A. digitalWrite() B. digitalRead() C. analogWrite() D. pinMode()

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: digitalRead() returns the logic state of a digital input pin.

Q16. Which Arduino function drives a digital output HIGH or LOW?

A. digitalRead() B. analogRead() C. digitalWrite() D. delay()

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: digitalWrite() sets a digital output to HIGH or LOW.

Q17. On a typical Arduino Uno, analogRead() uses a:

A. 2-bit ADC B. 4-bit DAC C. 16-bit timer only D. 10-bit ADC

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: The Uno's ADC is 10-bit, giving 1024 quantization levels, normally represented from 0 to 1023.

Q18. A microcontroller generally integrates:

A. CPU, memory and peripherals on one chip B. only an ALU C. only RAM D. only a communication cable

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Microcontrollers integrate a processor core with memory and peripherals such as GPIO, timers and communication interfaces.

Q19. A microprocessor differs from a typical microcontroller mainly because it:

A. always has built-in Wi-Fi B. usually relies more heavily on external memory and peripherals C. cannot execute programs D. contains no CPU

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A conventional microprocessor is primarily a CPU and generally uses external memory and peripheral chips, whereas a microcontroller integrates many of them.

Q20. GPIO stands for:

A. General Processor Internet Operation B. Graphical Port Input Only C. General Purpose Input/Output D. Global Peripheral Interface Output

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: GPIO means General Purpose Input/Output and refers to configurable digital pins used to interface with external circuits.

Q21. Which communication interface is commonly used for a single master with multiple addressed peripheral devices using two wires?

A. UART B. PWM C. GPIO only D. I2C

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: I2C uses SDA and SCL and supports addressed devices on a shared two-wire bus.

Q22. ESP32 is widely known for integrating:

A. Wi-Fi and Bluetooth connectivity B. only analog circuitry C. only a mechanical relay D. only USB storage

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Many ESP32 variants integrate Wi-Fi and Bluetooth/BLE, making them popular for connected embedded applications.

Q23. Which feature is generally associated with ESP32 rather than the classic Arduino Uno?

A. 8-bit AVR core B. Integrated Wi-Fi C. ATmega328P D. 10-bit ADC only

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: ESP32 devices provide integrated wireless connectivity, while the classic Uno does not have built-in Wi-Fi or Bluetooth.

Q24. A relay in a home-automation circuit is commonly used to:

A. measure humidity B. increase sensor resolution C. switch a higher-power load using a control signal D. convert AC to DC automatically

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: A relay provides electrical isolation and allows a low-power controller output to control a higher-power circuit, within its ratings.

Q25. A smart irrigation system most directly uses soil-moisture data to:

A. increase Wi-Fi password strength B. measure CPU temperature only C. replace all valves with LEDs D. decide when irrigation is needed

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Soil-moisture sensing provides feedback that can be used to start or stop irrigation based on the moisture threshold.

Q26. A smart health-care IoT device may commonly monitor:

A. heart rate or body temperature B. only internet speed C. only room lighting D. only vehicle speed

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Wearable and remote-monitoring devices can collect physiological variables such as heart rate, temperature and oxygen saturation.

Q27. A smart lighting system often uses a light sensor to:

A. measure water pressure B. adjust lighting according to ambient illumination C. control engine speed D. store web pages

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Ambient-light sensing can be used to switch or dim lights according to available natural illumination.

Q28. Smart parking systems commonly use sensors to determine:

A. the user's blood pressure B. soil pH C. whether parking spaces are occupied D. CPU instruction length

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Parking sensors detect vehicle presence in individual spaces and can report availability to a controller or application.

Q29. MQTT is widely used in IoT because it is:

A. a mechanical sensor B. a programming language for PLCs C. a type of battery D. a lightweight publish/subscribe messaging protocol

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: MQTT uses a lightweight publish/subscribe model suited to devices and networks with limited resources.

Q30. In MQTT, a broker primarily:

A. routes messages between publishers and subscribers B. measures temperature C. powers sensors D. compiles Arduino code

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: The MQTT broker receives published messages and forwards them to subscribers according to topics.

Q31. Edge computing in IoT means:

A. sending every raw sample to a distant cloud before any action B. processing some data close to where it is generated C. removing all sensors D. using only paper records

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Edge computing places computation near devices, reducing latency, bandwidth use and dependence on remote processing.

Q32. Which is an example of an IoT gateway function?

A. casting metal parts B. printing circuit boards C. protocol conversion and data aggregation D. measuring only voltage

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: A gateway can aggregate sensor data and translate between local device protocols and IP/cloud protocols.

Q33. A transducer that converts electrical energy into mechanical motion is generally an:

A. ADC B. thermistor C. LDR D. actuator

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Actuators convert electrical/control energy into physical effects such as motion.

Q34. An LDR changes its resistance mainly with:

A. incident light intensity B. sound frequency C. water pressure D. magnetic flux only

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: A light-dependent resistor changes resistance with illumination and is therefore useful for light sensing.

Q35. An ultrasonic sensor estimates distance using:

A. change in electrical resistance due to light B. time of flight of acoustic pulses C. thermoelectric voltage D. radioactive decay

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: The sensor sends an ultrasonic pulse and determines distance from the echo time and known speed of sound.

Q36. A PIR sensor is primarily used to detect:

A. soil moisture B. barometric pressure C. infrared radiation changes associated with moving people D. electrical resistance only

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: PIR sensors detect changes in infrared radiation from warm moving objects and are common in occupancy/security systems.

Q37. In an IoT architecture, why is a gateway often placed between constrained sensor nodes and the cloud?

A. To eliminate all sensor calibration B. To replace every actuator with a router C. To prevent any device communication D. To perform aggregation, protocol translation and local processing

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: A gateway can aggregate data, translate protocols, provide security functions and perform local processing before forwarding information to cloud services.

Q38. Which statement best distinguishes a sensor from a transducer?

A. A transducer broadly converts one form of energy/quantity to another; a sensor detects a physical quantity for measurement B. A sensor can never produce an electrical signal C. A transducer is always a digital device D. There is no conceptual distinction in measurement systems

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Sensor and transducer are often used interchangeably in IoT, but transducer emphasizes energy/quantity conversion while a sensor emphasizes detection/measurement.

Q39. For a resistive sensor used with an ADC, a voltage-divider interface is useful because it:

A. converts Wi-Fi into Bluetooth B. converts resistance variation into a measurable voltage variation C. removes the need for a power supply D. guarantees zero measurement error

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A voltage divider maps resistance changes to voltage changes, allowing a microcontroller ADC to quantify the sensor output.

Q40. A 10-bit ADC has how many distinct output codes?

A. 1000 B. 512 C. 1024 D. 2048

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: An N-bit ADC has 2^N codes. For 10 bits, 2^10 = 1024 codes, normally numbered 0 through 1023.

Q41. If an Arduino input is configured with INPUT_PULLUP, an externally connected pushbutton to ground will normally read:

A. LOW when released and HIGH when pressed B. HIGH in both states C. LOW in both states D. HIGH when released and LOW when pressed

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: The internal pull-up biases the input HIGH; pressing a switch connected to ground pulls it LOW.

Q42. Why is debouncing required for a mechanical pushbutton?

A. Mechanical contacts can produce multiple rapid transitions during one press B. The button generates Wi-Fi packets C. The ADC cannot read digital signals D. Debouncing increases supply voltage

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Contact bounce creates several rapid HIGH/LOW transitions, which software or hardware debouncing filters into one intended event.

Q43. Which ESP32 capability is especially useful for a sensor node that must connect directly to a wireless LAN?

A. Only an external Ethernet transformer B. Integrated Wi-Fi C. A mechanical relay D. A thermocouple

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Integrated Wi-Fi lets many ESP32 boards communicate with an access point without a separate Wi-Fi module.

Q44. A finite-state machine is useful in home automation because it:

A. guarantees unlimited memory B. replaces all sensors C. represents operating modes and defined transitions based on events D. eliminates communication protocols

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: States such as HOME, AWAY and NIGHT can have explicit transition rules based on occupancy, time or commands.

Q45. For battery-powered IoT nodes, deep sleep is primarily used to:

A. increase ADC resolution B. increase motor speed C. improve Ethernet bandwidth D. reduce energy consumption between measurement/communication events

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Deep-sleep modes turn off or reduce many functions so the device consumes much less energy while inactive.

Q46. A common reason to perform edge filtering before cloud transmission is to:

A. reduce noise and unnecessary data traffic B. increase the number of sensors automatically C. remove the need for a controller D. make every signal analog

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Filtering can suppress noise and event detection can prevent redundant samples from consuming bandwidth and cloud resources.

Q47. In a smart irrigation system, hysteresis around a moisture threshold helps to:

A. increase soil salinity B. prevent rapid ON/OFF switching near the threshold C. disable the pump permanently D. convert analog data to Wi-Fi

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: If separate ON and OFF thresholds are used, small fluctuations near one threshold do not cause repeated pump switching.

Q48. For safe control of a water pump, a controller output should generally drive:

A. the pump directly from a GPIO pin B. an ADC input C. an appropriately rated driver/relay or power stage rather than the pump directly D. a pull-up resistor only

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Microcontroller GPIO pins cannot safely supply typical pump current. A rated driver stage provides current capability and protection.

Q49. Which communication pattern is native to MQTT?

A. Token ring only B. Circuit switching C. Polling by mechanical relay D. Publish/subscribe

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: MQTT uses topics with publishers sending messages and subscribers receiving messages through a broker.

Q50. If a smart-health sensor loses network connectivity, a robust design can:

A. buffer measurements locally and upload them when connectivity returns B. discard all measurements immediately C. increase LED brightness D. change the patient's sensor type

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Local buffering prevents data loss during temporary network outages and supports delayed synchronization.

Q51. Why is galvanic isolation useful when a microcontroller controls a mains load?

A. It increases ADC bit depth B. It can separate low-voltage control circuitry from the hazardous power circuit C. It makes a sensor wireless D. It removes all fuses

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Isolation reduces the direct electrical connection between low-voltage electronics and hazardous/high-energy circuits; appropriate protection is still required.

Q52. An Arduino Uno 10-bit ADC uses a 5.0 V reference. What digital code is approximately obtained for an input of 2.5 V?

A. 256 B. 768 C. 512 D. 1023

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: For an ideal 10-bit ADC, code ≈ Vin/Vref × 1023 = 2.5/5 × 1023 ≈ 512.

Q53. A digital temperature sensor sends 20 samples per second. How many samples are produced in 5 minutes?

A. 300 B. 1000 C. 12000 D. 6000

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Samples = 20 samples/s × 5 × 60 s = 6000 samples.

Q54. An IoT node transmits 80 bytes every 10 seconds. Ignoring protocol overhead, how many bytes are transmitted in 1 hour?

A. 28,800 B. 8,000 C. 2,880 D. 288,000

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: There are 360 ten-second intervals in an hour, so 80 × 360 = 28,800 bytes.

Q55. A soil-moisture sensor outputs 1.0 V at dry condition and 3.0 V at wet condition. If the ADC input is 2.0 V and the relation is linear, the normalized moisture fraction is:

A. 0.25 B. 0.50 C. 0.75 D. 1.00

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: The fraction is (2.0−1.0)/(3.0−1.0)=1/2=0.50.

Q56. A 12-bit ADC has a 3.3 V reference. What is the approximate voltage represented by code 2048 using code/Vref × Vref approximation?

A. 0.805 V B. 2.475 V C. 1.65 V D. 3.30 V

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: 2048 is approximately half of 4096 codes, so the corresponding input is about 3.3/2 = 1.65 V.

Q57. A smart light is rated 12 W and operates for 10 hours per day. What energy does it consume per day?

A. 12 Wh B. 1.2 Wh C. 1200 Wh D. 120 Wh

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Energy = power × time = 12 W × 10 h = 120 Wh.

Q58. A 5 V sensor draws 20 mA. What is its electrical power consumption?

A. 0.10 W B. 0.025 W C. 0.40 W D. 100 W

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: P = VI = 5 × 0.020 = 0.10 W.

Q59. A battery has a nominal capacity of 2000 mAh. An IoT node draws 100 mA continuously. Ignoring losses, its ideal operating time is:

A. 2 h B. 20 h C. 200 h D. 0.05 h

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Ideal time = capacity/current = 2000 mAh / 100 mA = 20 h.

Q60. A parking sensor reports an occupied space every 4 seconds. How many reports are generated in 30 minutes?

A. 120 B. 900 C. 450 D. 720

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Thirty minutes is 1800 s. Reports = 1800/4 = 450.

Q61. An ESP32 application samples a sensor at 100 Hz. How many samples are collected in 2.5 minutes?

A. 250 B. 6,000 C. 25,000 D. 15,000

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: 2.5 min = 150 s. Samples = 100 × 150 = 15,000.

Q62. A 16-channel smart-light controller uses 2 bits to encode each of four lighting states. How many bits are needed for one complete state record of all 16 channels?

A. 32 bits B. 16 bits C. 64 bits D. 8 bits

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Each channel needs 2 bits, so 16 × 2 = 32 bits.

Q63. An ultrasonic sensor measures an echo time of 5.8 ms. If the speed of sound is 340 m/s, what is the approximate one-way distance?

A. 1.972 m B. 0.986 m C. 0.494 m D. 5.8 m

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: The pulse travels to the object and back, so d = vt/2 = 340 × 0.0058 / 2 ≈ 0.986 m.

Q64. A relay coil is driven from 5 V and draws 70 mA. What is the coil power?

A. 0.014 W B. 3.5 W C. 0.35 W D. 70 W

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: P = VI = 5 × 0.070 = 0.35 W.

Q65. An ADC has 1024 codes over 0–5 V. What is its approximate voltage resolution per code?

A. 0.488 mV B. 48.8 mV C. 2.44 V D. 4.88 mV

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Resolution ≈ 5/1024 V = 0.0048828 V ≈ 4.88 mV per code.

Q66. A smart irrigation pump runs for 6 minutes each hour. Over 8 hours, how many minutes does it operate?

A. 48 min B. 14 min C. 64 min D. 360 min

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: The pump runs 6 min/hour × 8 hours = 48 minutes.

Q67. A 10-bit ADC with a 3.3 V reference receives 1.65 V. The ideal output code is approximately:

A. 256 B. 512 C. 768 D. 1023

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: The input is half the reference, so code ≈ 0.5 × 1023 ≈ 512.

Q68. An ESP32 sends a 100-byte payload every 2 seconds for 10 minutes. Ignoring protocol overhead, total payload is:

A. 3,000 bytes B. 60,000 bytes C. 30,000 bytes D. 6,000 bytes

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Ten minutes is 600 seconds, giving 600/2 = 300 transmissions. 300 × 100 = 30,000 bytes.

Q69. A soil sensor has a 0–3.0 V output corresponding linearly to 0–100% moisture. At 2.1 V, the indicated moisture is:

A. 30% B. 63% C. 90% D. 70%

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Moisture = 2.1/3.0 × 100 = 70%.

Q70. A 3.3 V GPIO drives an LED through a 220-ohm resistor. Assuming an LED drop of 2.1 V, the current is approximately:

A. 5.45 mA B. 15 mA C. 10 mA D. 1.2 mA

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: I = (3.3−2.1)/220 = 1.2/220 ≈ 0.00545 A = 5.45 mA.

Q71. A sensor consumes 40 mA for 0.5 s every 10 s and is otherwise off. What is its average current, ignoring sleep current?

A. 4 mA B. 2 mA C. 20 mA D. 0.5 mA

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Duty cycle = 0.5/10 = 0.05. Average current = 40 × 0.05 = 2 mA.

Q72. A smart-light network contains 24 lamps, each consuming 8 W when ON. If 75% are ON simultaneously, total power is:

A. 192 W B. 72 W C. 144 W D. 18 W

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: ON lamps = 24 × 0.75 = 18. Power = 18 × 8 = 144 W.

Q73. An ultrasonic sensor returns an echo after 11.76 ms. With sound speed 340 m/s, the target distance is approximately:

A. 4.0 m B. 1.0 m C. 11.76 m D. 2.0 m

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Distance = vt/2 = 340 × 0.01176 / 2 ≈ 2.0 m.

Q74. A battery-powered node draws 120 mA for 2 minutes every 20 minutes and 2 mA otherwise. Its average current is approximately:

A. 13.8 mA B. 12 mA C. 24 mA D. 4 mA

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Average = 120×(2/20) + 2×(18/20) = 12 + 1.8 = 13.8 mA.

Q75. For an IoT system controlling a safety-critical actuator, which architecture best limits dependence on cloud availability?

A. Send every control decision to the cloud with no local fallback B. Use local edge control for time-critical decisions and cloud for supervision/analytics C. Disable local sensing D. Use only a dashboard without feedback

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Time-critical and safety-related actions should have local control and fail-safe behavior; the cloud can support monitoring, history and higher-level analytics.

Q76. A sensor network experiences packet loss that is correlated with high motor current. The most appropriate first engineering investigation is:

A. changing the database table name B. increasing the font size of the dashboard C. electromagnetic interference, grounding and power integrity near the motor and radio D. removing sensor calibration

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Motor switching can create conducted/radiated EMI and supply disturbances. Checking wiring, grounding, decoupling and physical separation is an appropriate first diagnosis.

Q77. In MQTT, QoS 1 provides:

A. exactly-once delivery with no protocol overhead B. no acknowledgement C. only local GPIO control D. at-least-once delivery, so a message may be delivered more than once

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: QoS 1 uses acknowledgement and can result in duplicate delivery; applications should tolerate or handle duplicates where necessary.

Q78. A retained MQTT message is useful when:

A. a new subscriber should receive the most recently retained value for a topic B. all historical messages must be replayed automatically C. the broker must power the sensor D. Wi-Fi must be disabled

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: A retained message lets a new subscriber obtain the latest retained state immediately after subscribing.

Q79. A smart-health wearable sends personally identifiable measurements to a cloud service. Which control most directly protects confidentiality in transit?

A. increasing ADC resolution B. authenticated encrypted communication such as TLS C. using a brighter status LED D. sampling less frequently

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: TLS can provide encryption and endpoint authentication for data transmitted between device/gateway and service, when correctly configured.

Q80. A sensor has random noise but negligible bias. Averaging repeated independent measurements generally:

A. increases noise by N B. removes all possible systematic errors C. reduces the standard deviation of the mean approximately in proportion to 1/sqrt(N) D. changes the sensor's physical range

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: For independent random noise, averaging N samples reduces the standard deviation of the mean by approximately sqrt(N), while systematic bias remains.

Q81. A control loop for irrigation has a very slow moisture response. Increasing controller sampling frequency alone will not necessarily improve performance because:

A. sampling frequency always determines plant growth B. ADC resolution becomes zero C. Wi-Fi bandwidth becomes infinite D. the plant-soil dynamics may dominate the response and excessive updates can cause unnecessary switching

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: The plant-soil system has slow dynamics. Control design must consider process response, hysteresis, delays and actuator constraints, not just sample rate.

Q82. A smart-lighting system uses occupancy and ambient light. During daylight, an occupied room should remain dim unless illumination falls below a threshold. This is an example of:

A. rule-based sensor fusion/control B. open-loop control with no sensing C. memory allocation D. ADC quantization

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: The decision combines multiple sensor conditions to determine the lighting command, which is a simple form of sensor fusion and rule-based control.

Q83. A 3.3 V microcontroller GPIO is not 5 V tolerant. Directly connecting a 5 V digital output can:

A. always improve logic noise margin safely B. exceed the input rating and potentially damage the GPIO; level shifting is appropriate C. reduce the 5 V signal to 0 V automatically D. increase ADC resolution

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A non-5-V-tolerant input should not be driven above its specified voltage. A suitable level shifter or divider/interface should be used.

Q84. For an analog sensor connected to an ADC, aliasing can occur when:

A. the sensor is perfectly static B. the GPIO is configured as output C. the signal contains frequency components above the Nyquist limit and is not adequately filtered D. the battery is fully charged

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Sampling above the Nyquist requirement is necessary but not sufficient; an anti-aliasing low-pass filter is commonly used to attenuate higher-frequency components.

Q85. A smart parking system uses multiple sensors whose clocks drift relative to each other. For reliable event correlation, it is useful to:

A. ignore time information entirely B. increase LED current C. remove all gateways D. synchronize timestamps or estimate clock offsets

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Common or corrected time bases allow events from different nodes to be aligned for occupancy and analytics.

Q86. A cloud-connected irrigation system loses WAN connectivity but still has local sensor and actuator access. A resilient design should:

A. continue local control using cached rules and synchronize data later B. stop irrigation regardless of soil state C. open the valve permanently D. erase sensor history

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Local autonomy provides continuity during network outages, while later synchronization restores cloud visibility.

Q87. An IoT device uses a bootloader to support firmware updates. A secure update mechanism should include:

A. accepting any unsigned binary from the network B. authenticated firmware and integrity verification before installation C. disabling rollback protection in all cases D. storing the password in source code

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Authenticity and integrity checks help prevent unauthorized or corrupted firmware from being installed.

Q88. A strain-gauge bridge has a very small differential output. A high common-mode rejection instrumentation amplifier is useful because:

A. it converts the bridge directly into Wi-Fi B. it eliminates the need for excitation C. it amplifies the small differential signal while rejecting common-mode voltage D. it guarantees zero thermal drift

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Instrumentation amplifiers are designed for accurate differential amplification with high input impedance and high common-mode rejection.

Q89. A transducer's static sensitivity is defined as:

A. maximum output voltage only B. ratio of noise to bandwidth C. time taken to boot the controller D. change in output per unit change in input

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Sensitivity is the slope of the input-output characteristic, i.e., change in output divided by change in measurand.

Q90. A high common-mode rejection ratio (CMRR) is especially important when:

A. a small differential sensor signal is superimposed on a larger common-mode voltage B. the sensor has no electrical output C. only a relay contact is used D. the microcontroller is asleep

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: High CMRR allows an amplifier to reject common-mode components while accurately amplifying the desired differential signal.

Q91. Why is an anti-aliasing filter placed before an ADC?

A. to increase GPIO current B. to attenuate frequency components that could alias into the sampled band C. to encrypt sensor data D. to create a digital clock

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: The filter limits the analog bandwidth before sampling so unwanted high-frequency components do not fold into lower frequencies.

Q92. A smart parking algorithm should distinguish sensor uncertainty from occupancy logic because:

A. uncertainty always means the sensor is broken B. occupancy has no relation to measurements C. measurement noise can otherwise cause false state changes near a threshold D. software cannot use thresholds

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Separating measurement processing from decision logic allows filtering, hysteresis and confidence rules to reduce false detections.

Q93. For an IoT system with intermittent connectivity, store-and-forward means:

A. discarding data when the network fails B. sending data only before sensing C. using a mechanical relay as memory D. buffering data locally and transmitting it when a connection becomes available

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Store-and-forward preserves locally collected data and forwards it after connectivity is restored.

Q94. A secure boot mechanism is intended primarily to:

A. ensure that only trusted/authenticated firmware is executed B. increase sensor sensitivity C. reduce ADC quantization D. control a relay coil

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Secure boot establishes a chain of trust so unauthorized firmware is rejected before execution.

Q95. In a distributed IoT system, least privilege means:

A. every device receives administrator access B. each device or service receives only the permissions required for its function C. all devices share one password D. security is delegated entirely to the sensor

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: Least privilege limits the impact of credential compromise or software faults by minimizing unnecessary permissions.

Q96. A Kalman filter is conceptually useful when:

A. only a binary LED is being driven B. there is no uncertainty C. a dynamic system is observed through noisy measurements and a model can predict its state D. the sensor has no time-varying state

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: Kalman filtering combines a system model and noisy observations to estimate hidden states under suitable assumptions.

Q97. A smart-health system should separate raw sensor data from clinical interpretation because:

A. raw data is always wrong B. clinical interpretation never needs evidence C. sensor calibration is unnecessary D. measurement data and clinical decisions have different validation, safety and responsibility requirements

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Raw measurements require technical validation, while clinical interpretation requires appropriate domain validation, safety controls and context.

Q98. A home-automation system uses a local controller for door locks while the cloud provides analytics. This architecture primarily demonstrates:

A. edge autonomy combined with cloud services B. cloud-only control C. sensorless automation D. analog-only processing

Check Answer

Correct Answer: A   |   Marks: 1

Explanation: Local control keeps time-critical functions available during network outages while cloud services provide storage and analytics.

Q99. A smart irrigation valve requires 500 mA but an MCU GPIO can safely source only 12 mA. The appropriate engineering solution is:

A. connect the valve directly to the GPIO B. use a transistor/MOSFET driver or rated driver module with suitable flyback protection C. use a pull-up resistor only D. increase the GPIO software delay

Check Answer

Correct Answer: B   |   Marks: 1

Explanation: A power driver stage supplies the valve current while the MCU controls it. Inductive loads also require suitable transient/flyback protection.

Q100. A 3.3 V, 12-bit ADC measures 2.475 V. The ideal ADC code is approximately:

A. 1024 B. 2048 C. 3071 D. 4095

Check Answer

Correct Answer: C   |   Marks: 1

Explanation: The fraction of full scale is 2.475/3.3 = 0.75. Thus code ≈ 0.75×4095 ≈ 3071.

Q101. A sensor node draws 10 mA continuously and 90 mA for 1 second every 30 seconds. Its average current is approximately:

A. 13.0 mA B. 10.0 mA C. 90.0 mA D. 12.67 mA

Check Answer

Correct Answer: D   |   Marks: 1

Explanation: Average current = 10 + (90−10)×(1/30) = 10 + 2.667 = 12.67 mA.