Your Answer : (Not Answered)

Correct Answer : D

The key names the thermistor as the highly sensitive transducer.

The passage defines sensitivity as the ratio of the change in output to the change in input. A thermistor's resistance changes by several percent for each degree Celsius (about -4 % per degree for a typical NTC type), which is far more than a thermocouple, whose output changes by only some tens of microvolts per degree. A potentiometer is a position transducer with a change per unit of travel set by its supply, and its output is not small-signal sensitive in the same way.

A photodiode is also very sensitive to light, which is why this item is a best-answer one; the key reads the question as being about temperature-type transducers, where the thermistor is the highly sensitive choice.

Your Answer : (Not Answered)

Correct Answer : C

The answer is (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii), as the key gives. Three pairs are firm and the fourth is forced.

A piezo-electric element converts pressure or force to charge, so (a) goes with pressure. A beta gauge measures thickness from how far a sheet absorbs beta radiation, so (c) goes with thickness. An LVDT (linear variable differential transformer) measures displacement, so (d) goes with displacement.

That leaves temperature for the foil strain gauge. A strain gauge normally measures strain, and through it force or pressure, and temperature enters only as an error to be compensated, so the pairing is the paper's forced match rather than a natural one. No other option can be consistent with the three firm pairs: option A makes the piezo-electric element a thickness sensor, option B makes the beta gauge a temperature sensor, and option D pairs every item wrongly.

Your Answer : (Not Answered)

Correct Answer : D

The best flow-meter for corrosive liquids is the magnetic flow-meter.

An electromagnetic flow-meter measures the voltage induced in a conducting liquid flowing through a magnetic field (Faraday's law). It has no moving parts and nothing obstructing the flow, and its tube can be lined with corrosion-resistant materials such as PTFE, so corrosive and dirty liquids do not damage it.

Displacement, piston type and turbine meters all have moving parts in contact with the liquid, which corrosive fluids would wear and attack.

Your Answer : (Not Answered)

Correct Answer : B

The keyed property is a large dynamic range.

Because MEMS sensors have very small moving masses, they combine high sensitivity with high resonant frequencies, and they can respond to signals over a wide range of amplitudes, from very small to large, before saturating, which is described as a large dynamic range.

Low sensitivity is the opposite of what miniaturisation gives. Their small mass gives a high, not very low, frequency response. High mechanical strength is not what follows from miniaturisation, since tiny structures are fragile and must be packaged to protect them.

Your Answer : (Not Answered)

Correct Answer : B

The sequence is Sensor, Data Acquisition, Communication, Cloud storage.

An IoT system starts at the physical world: sensors measure quantities such as temperature or motion. A data acquisition stage digitises and conditions those readings, a communication module (Wi-Fi, cellular, LoRa and so on) sends them over the network, and the data are stored in the cloud, where they can then be analysed.

The other options put cloud storage, data acquisition or communication first, before any sensor has produced data, which reverses the flow of information.

Your Answer : (Not Answered)

Correct Answer : C

The functional elements of MEMS are of the order of \(1 \times 10^{-6}\) m, a micrometre.

Micro-electro-mechanical systems combine tiny mechanical parts (beams, membranes, gears) with electronics on a chip. Their functional elements typically measure from about 1 to 100 micrometres, which is why they are called micro systems.

\(1 \times 10^{-3}\) m (a millimetre) is the scale of the whole device or package, and \(1 \times 10^{-9}\) m (a nanometre) is the scale of NEMS and nanotechnology. \(1 \times 10^{6}\) m is a thousand kilometres.

Your Answer : (Not Answered)

Correct Answer : B

The technology associated with IoT implementation is big data analytics.

An Internet of Things system links large numbers of sensors and devices that continuously send data to the cloud. The value lies in analysing that huge, fast-flowing and varied data, which is what big data analytics provides: storage, processing and machine-learning tools that turn sensor readings into decisions and predictions.

High power drivers and cryogenics are unrelated to IoT, whose devices are typically low-power. LTCC (low temperature co-fired ceramic) is a packaging and substrate technology for RF modules, not something that characterises IoT.

Your Answer : (Not Answered)

Correct Answer : B

The key gives sensing, data acquisition, conversion and communication.

An IoT sensor node starts by sensing the physical quantity. Data acquisition then collects the sensor output and conditions it, the signal is converted into digital form (analog to digital conversion), and the digital data is finally sent to the network by the communication module. Any order that puts communication before the data exists in digital form, as in option D, cannot work, and a chain that starts with data acquisition, as in option A, has nothing to acquire yet.

The difference between B and C is only whether acquisition comes before conversion. Descriptions of the IoT sensing chain differ on this, and I could not find a source that settles it, so B stands on the University's key and on the reading that acquisition (collecting and conditioning the signal) precedes digitisation.

Your Answer : (Not Answered)

Correct Answer : C

The piezoelectric substances are 1, 2 and 3.

Barium titanate and lead titanate are perovskite ferroelectric ceramics with strong piezoelectric effects, and lead zirconate is the other component of lead zirconate titanate (PZT), the most widely used piezoelectric ceramic. These are the materials used in ultrasonic transducers, buzzers and accelerometers.

'Cadmium and sulphate' is not a piezoelectric material; the cadmium compound with piezoelectric properties is cadmium sulphide, a semiconductor, and a sulphate salt is not used as a transducer. So every option including 4 is wrong.

Your Answer : (Not Answered)

Correct Answer : C

The amplifier gain is 2.5 mV/pC.

The overall sensitivity is the product of the transducer's sensitivity and the amplifier's gain, so the amplifier gain is the overall gain divided by the transducer's:

\[ \begin{aligned} G &= \frac{50\ \text{mV/N}}{20\ \text{pC/N}} \\ &= 2.5\ \text{mV/pC} \end{aligned} \]

The newtons cancel, leaving millivolts per picocoulomb, the natural unit for a charge amplifier. 1 mV/pC and 1.5 mV/pC would give an overall gain of only 20 or 30 mV/N, and 4 mV/pC would give 80 mV/N.

Your Answer : (Not Answered)

Correct Answer : B

The official key is S2 and S3: the gauges are brittle and temperature sensitive, and they show poor linearity.

These two points describe semiconductor strain gauges, which have a large gauge factor but whose resistance changes non-linearly with strain, drift with temperature and are brittle and hard to bond. Sources found for the search agree on brittleness, temperature sensitivity and non-linearity.

What could not be confirmed: sources disagree on the cost of semiconductor gauges, which some call low and some high, and 'low fatigue life' (S1) was not found among the usual listed drawbacks. The key's S1-free answer, S2 and S3, is therefore kept; options containing S1 are rejected on that basis.

Your Answer : (Not Answered)

Correct Answer : C

A strain gauge is a passive device that converts mechanical displacement into a change of resistance.

A strain gauge is a fine wire or foil grid bonded to a surface. When the surface is strained, the grid stretches or compresses, changing its length, cross-section and resistivity, and so its resistance; the gauge factor relates the fractional change in resistance to the strain.

It is passive because it generates no energy of its own: an external excitation, usually a Wheatstone bridge, is needed to turn the resistance change into a voltage. The options calling it active describe a self-generating transducer such as a thermocouple or piezoelectric crystal, and 'electrical displacement' is not what it senses.