Prove svolte di Automotive Electronics Systems con giustificazioni 2026

AUTOMOTIVE ELECTRONICS

SYSTEMS

6 CFU

LM INGEGNERIA DEL VEICOLO

DOMANDE A SCELTA MULTIPLA GIUSTIFICATE

AGGIORNATE AD APRILE 2026

Da foto tracce

Exam ID = 38

1) Which of the following is true for an inductor?

No option is true

• All options are true

• It is a reactive component

• Its impedance is purely imaginary

• Its impedance is always positive

•

it stores magnetic energy with purely imaginary impedance (jwL) and an always positive

reactance (wL)

• All answers are correct

• Yes

• Yes, the inductor has an imaginary impedance, so it’s reactive

• Yes, its impedance is ˙Z = jωL

• Yes, > 0 and L >0

ω

2) Thermistors are

Available in the NTC and PTC varieties

• Very precise but expensive

• Based on the properties of a pair of metals

• No option is true

• Very linear

•

PTC based on Si with a quadratic dependance of the resistance on the temperature, NTC based

on metal-oxides with exponential response. They are cheap and precise, they are based on

semiconductor not on a pair of metals

• Yes, Positive and Negative T coefficient (PTC have a quadratic dependance from the

temperature while NTC have an exponential one)

• No, are made of semiconductors so they are cheap

• No, they are made of semiconductors, not metals (thermocouples are based on the

properties of a pair of metals)

• There’s a correct answer

• There’s at least a wrong answer

3) An ideal op-amp

Has infinite open loop bandwidth

• No option is true

• Has infinite input impedance

• Has infinite open loop gain

• All options are true

•

a real op-amp has finite gain, defined bandwidth and a finite gain

• Yes, to have a constant gain for all frequency

• All answers are correct

• Yes, to have zero input current

• Yes, to work better as an amplifier

• Yes

4) The Shannon-Nyquist theorem

States that non-uniform sampling is impossible

• All options are true

• Requires the input signal bandwidth to be not larger than half of the sampling frequency

• Can only be proven for discrete signals

• No option is true

•

if the Nyquist theorem is respected, there isn't the aliasing.

• No, the jitter error makes uniform sampling impossible in reality (The theorem specifically

describes the requirements for uniform sampling, but it doesn’t say that is impossible)

• There’s a correct answer

• Yes, to avoid aliasing fn = fs/2

• No, it’s valid for all type of limited signals

• There’s at least a wrong answer

5) The ALU

Is typically asynchronous

• Performs mathematical and logical operations

• No option is true

• Supports any kind of instruction

• Is devoted to the communication between the memory and the CPU

•

the ALU can handle mathematical and logical operations that can produce status information

used by the processor. most ALUs are synchronous and can’t communicate between memory

and the CPU

• No, it’s synchronized to the clock signal

• Yes, the ALU can perform only mathematical (add, subtract, ...) or logical operations

(AND,OR, NOT)

• There’s a right answer

• No, it supports only codes and datas

• No, that’s the role of the memory controller

6) In an H bridge circuit

The load can be supplied only positive voltages

• It is impossible to use all n-MOSFETS

• It is possible to set the load in free run

• There are 4 equivalent configuration for braking

• The load cannot be short circuited

•

it can set a DC motor in free run by opening all 4 switches. The H-bridge can have a reverse

polarity and 2 “brake mode”, moreover, all MOSFETC can be used.

• No, also negative voltages to rotate in opposite direction

• No, you can use all n-MOSFETs driving the gates of the high side with gate drivers, it’s a

cheaper solution

• Yes, opening all the switches

• No, just 2 short circuiting the motor (S1-S3 closed or S2-S4 closed with the opposites

open)

• Yes, that’s the regenerative braking

7) The thermal resistance of a thermal actuator

Needs to be as low as possible

• Controls the dynamics with which thermal equilibrium is reached

• Is measured in W/K

• All options are true

• No option is true

•

thermal resistance is measured in K/W (not W/K) and determines the steady-state temperature

gain, whereas the system's dynamics are controlled by the thermal time constant (R_th C_th)

a) No, it must be as high as possible

• b) No, it tells the temperature increase per unit of power dissipation, so a static dynamic

• c) No, is measured in K/W

• d) All answers are wrong

• e) Yes.

•

8) In open-loop control mode, the ECU must

No option is true

• Choose the correct A/F ratio form a look-up table

• Acquire information from multiple sensors

• Wait for the EGO sensor to be warmed up

• All options are true

•

in open-loop mode the ECU must adjust the a/f ratio and regulate the spark timing while

waiting until the EGR and EGO are warm enough

• All answers are correct

• Yes, to achieve the best fuel economy and emissions

• Yes, it detects information from the engine to choose the correct amount of fuel from a

ROM memory

• Yes, or the sensor won’t work properly

• Yes

9) In the ABS

The system forces the slip to be always close to 1

• All options are true

• The lateral friction coefficient is reduced by electronic control

• No option is true

• The valves are mechanically controlled devices

•

the ABS maximes the brakes efficiency by disconnecting the brake from the pedal when the

wheel is sliding

• No, you must stay away from slip 1 (skidding condition)

• There’s at least a wrong answer

• No, you never want to reduce lateral grip coefficient

• Yes

• No, valves are solenoids so magnetically controlled

Exam ID = 48

1) Which of the following is true for a capacitor?

Current can flow only when voltage stays the same over time

• For a fixed voltage over time, a larger capacitance implies a larger current through the

• coactor

Current can flow only when voltage changes over time

• For a fixed current over time, a larger capacitance implies a larger voltage rate of change

• over me

No option is true

• . If voltage is fixed, current is zero and A larger C would lead to a smaller rate of change

=

for a fixed current.

• No, when voltage stays constant, current cannot flow I = CdV/dt

• No, for fixed voltages, a larger capacitance implies a larger charge on the capacitor Q =

CV

• Yes, I = CdV/dt

• No, for fixed currents, a larger capacitance implies a smaller voltage rate of change over

time I/C =dV/dt

• There’s a correct answer

2) Piezoelectricity

No option is true

• All options are true

• Can be used to engineer sensors but not actuators

• Is the property for which the resistivity of a material changes upon deformation

• Is a reversible phenomenon

•

piezoelectricity materials generate a voltage if deformed and vice versa and they can be used

both as sensor and as actuators

• There’s a correct answer

• There’s at least a wrong answer

• No, piezoelectricity is a reversable phenomenon so it can be used also for actuators

• No, that’s piezoresistivity

• Yes, indeed can be exploited to make both sensors and actuators

3) A buck converter

Can theoretically reach 100% efficiency

• Always allows bidirectional energy flow

• Is an inductor-less DC-DC converter

• Has its output voltage only dependent on the switching frequency in continuous mode

• Can perform step-up conversion

•

the non ideal components make the efficiency drop. It is a step-down converter and it requires

an inductor to store energy. In continuous mode, the output depends primarily on the Duty

Cycle (D), not the frequency.

• Yes, it has no dissipative components so can theoretically reach 100% efficiency

• No, the buck converter has an inductor that plays a key role

• No, bidirectional energy flow is possible for the bidirectional converter that has 2 switches,

the buck has only 1

• No, output voltage depends mostly on the duty cycle Vout/Vin = D

• No, it perform step-down convertion, step-up is characteristic of the Boost converter

4) The phenomenon of aliasing

Arises when two sampling circuits try to simultaneously sample the same input

• No option is true

• Can be prevented by using non-uniform sampling

• Happens when sampling at a too low sampling frequency

• Is a consequence of the Shannon-Nyqusit theorem being satisfied

•

Aliasing occurs when the sampling frequency is lower than the Nyquist rate (fns>fs/2), causing

spectral replicas to overlap.

• No, is a consequence of Shannon Nyquist theorem NOT being satisfied

• No, arises only when the sampling frequency is too low

• Yes, by the Shannon-Nyquist theorem sampling frequency must be twice the input signal

bandwith

• No, can be attenuated with an anti-aliasing filter (low-pass) or avoided satisfying Shannon

Nyquist theorem

• There’s a correct answer

5) The AND gate

Has three logic outputs

• Is a three-state logic gate

• Has only one input combination for which the output is logic zero

• Requires just one logic input

• Has only one input combination for which the output is logic one

•

output line will be at logic 1 level only if all of its inputs are at logic 1 level. An AND gate have

only 1 output, the one input combination for logic 0 is a characteristic held by the OR gate.

No, has one output that can be 0 or 1

o No, has 4 possible combinations 11????- (is a binary logic device with two states (0 and 1)

o No, output is logic zero for 3 combinations (A=B=0; A=1, B=0; A=0, B=1)

o No, it requires 2 logic inputs

o Yes, the combination A=B=1

o

6) The Safe Operating Area

Is fixed for all relevant use and load conditions

• Is typically larger for BJTs than for MOSFETS

• Defines which pulse timing can be given to the transistor

• Is a region of the input characteristics of transistors

• No option is true

•

SOA tells you which combinations of voltage, current, power, and pulse duration are allowed

without damaging the transistor and it changes based on some variables (temperature, ecc).

Generally MOSFETs have a larger SOA in spite of BJT.

No, the SOA depends on temperature, pulse duration, and operating mode

o No, MOSFETs transistors have a larger SOA because BJTs have a positive dependence of

o the collector current on temperature

No, defines the maximum current, voltage and power that the transistor can withstand

o without damaging

No, is a region of the output characteristics of the transistor

o Yes

o

7) In a DC motor

No option is true

• The commutator avoids the motor being stuck

• The commutator avoids the possible free run of the motor

• The current frequency controls the torque

• The voltage frequency controls the rotor speed

•

the commutator keep the rotation of the coil in the right way. The voltage/current magnitude

controls speed/torque

There’s a right answer

o Yes, that’s the main characteristic of a DC motor

o No, it can be made also with electromagnets (it allows the motor to move in the right

o direction without interruptions)

no, current and magnetic field magnitude controls the torque

o no, voltage magnitude controls the rotor speed

o

8) Fuel injection is controlled by means of

A digital-like solenoid valve

• An inductor-activated pintle with a spring system

• All options are true

• No option is true

• PWM control

•

the magnetic field generated by the solenoid pulls up the pintle and the PWM control regulate

the amount of fuel

• Yes, the actuator can assume only 2 positions when magnetic field is present or not

• Yes, when current flows in the coil the magnetic field affects the pintle and pulls it up

compressing the spring

• Yes

• All answers are right

• Yes, to control the mean value of the fuel

9) The warm-up phase

All options are true

• Switches to open-loop mode when the engine temperature is beyond a critical value

• Checks for the correct A/F ratio in a memory depending on the engine temperature

• Provides a varying but always rich A/F ratio depending on engine temperature

• No option is true

•

during the engine warm-up mode, the ECU retrieves the target air-fuel (A/F) ratio from a ROM

based on the engine temperature sensor's output. It provides a varying but rich A/F ratio

(typically between 2:1 and 12:1) to facilitate heating, and once the coolant temperature exceeds

a specific value, the system switches to open-loop mode.

• Yes

• Yes, that’s the purpose of the warm-up phase, increasing the engine temperature

• Yes, it checks in a ROM memory the correct amount of fuel (so A/F ratio) to be injected in

the engine to increase the temperature

• Yes, the A/F ratio can varies from 2:1 to 12:1 which is rich

• All answers are right

Exam ID = 13

1) Which of the following is true for a diode?

All options are true

• It allows a significant current flow when reverse-biased

• In reverse bias, it can be reasonably well approximated to a short circuit

• For silicon diodes, if the applied voltage is larger than approximately 0.7V there is a

• behavioral change in its I-V relation

No option is true

•

the current increases very quickly if the voltage is more than 0.7V. in reverse bias the current is

very small and behaves like an open circuit

All answers are wrong

o There is a correct answer

o No, when reversed bias it doesn’t allow any current flow

o Yes, there is a significant change beyond 0.7V

o No, can be approximated to an open circuit

o

2) Strain gauges are

No option is true

• Subject to thermal issues

• All options are true

• Strain sensors

• Based on the change in resistance with the geometry

•

Strain gauges measure the deformation of an object and if temperature changes, the volume of

the object, and of the strain gauge, changes as well, moreover, if the cross section and the

length changes, also the resistance changes

All answers are correct

o Yes, they are made of resistors that are sensitive to temperatures

o Yes

o Yes, strain gauges are used also for strain sensors

o Yes, R = R0(1+Gϵ) with = l−l0/l0

o ϵ

4) The successive approximations A/D converter

All options are true

• Needs to run as many iterations as the resolution in bits

• Needs a DAC to work correctly

• Is based on the binary search algorithm

• Employs a comparator

•

DAC and comparator are included in the circuit and it is based on binary search algorithm wich

re-iterates the mechanism to a single band, completing the A/D conversion

Yes

o Yes, each iteration solves one bit

o Yes, to create an output trial DC voltage that will be compared to the input signal

o Yes, it search one bit per step (It works by testing one bit at a time to see if the input

o voltage falls in the upper or lower half of the remaining voltage range)

Yes, to compare the input voltage to the voltage exiting the DAC if is higher or lower

o

5) A PISO

Is a level triggered circuit

• Is a kind of flip-flop

• Is a shift register that allows to serialize parallel data

• Uses RS latches

• Has each flip-flop output connected to the next flip-flop input

•

the PISO loads multiple bits in parallel and then shifts them out one bit at a time, converting

parallel data into serial data.

No, is an edge triggered circuit

o No, is a register composed of flip-flops

o Yes, Parallel-IN Serial-OUT

o No, it uses flip-flops

o No, each flip-flop output is connected to an AND gate

o

6) In an n-MOSFET

The gate is internally short-circuited to the drain

• The current flows from the source to the drain

• The threshold voltage is larger than the overdrive voltage

• There are 2 working regions

• No option is true

•

the gate is isolated, the current flows from drain to source, there are 3 working regions and Vgs

– Vth = Voverd

No, it’s the bulk to be short-circuited to the source (no current flows though the gate

o because the gate is electrically isolated from the rest of the transistor)

No, current flows from drain to source

o No, VOD is how far above the threshold voltage you bias the transistor VOD = VGS −VTH

o No, there are 3 operationg regions (Cut-off, Saturation and Triode)

o Yes

o

8) The knock sensor

Can be piezoelectric or piezoresistive

• Needs a high-Q band pass filter

• Induces current in an inductor when knocking occurs

• All options are true

• Is typically magnetostrictive

•

it limits the increasing cylinder's pressure

Yes, also piezo sensors to sense pressure rapid rises

o Yes, to filter unwanted components and vibrations

o Yes, the magnetic field induces a current in an inductor to retard the ignition

o Yes

o Yes, to associates pressure variations to a magnetic field variation that induces a current

o in an inductor

9) The start-up phase

Checks for the correct A/F ratio in a memory depending on the engine temperature

• All options are true

• Provides an optimized A/F ratio depending on engine temper