11. Thermodynamics of transport processes
D
E
Which one of the following statements is FALSE?
In mechanics, all frictionless processes are irreversible.
Dissipative processes are irreversible.
Heat energy is not a distinct energy type.
Energy transfer between a system and its surroundings that is not a heat transfer,
is called work.
The heat energy and work are not state functions.
2
A
B
C
D
E
Which one of the following quantities is NOT an extensive parameter?
mass
heat
volume
entropy
temperature
3
A
B
C
D
E
Which statement is CORRECT for the 1st principle of thermodynamics?
The total amount of energy of isolated system is increasing.
It is an extension of the energy conservation principle on systems, which are in
thermal equilibrium with their environment.
The change of the internal energy is equal to the product of the work and the heat.
It is possible to make the first kind of perpetuum mobile.
The change of the internal energy is equal to the ratio of the work and the heat.
4
A
B
C
D
E
If pressure and enthalpy are constants, the criteria for spontaneous process is…
entropy (S) increase; dS > 0
internal enegy (U) decrease; dU < 0
Gibbs free energy (G) decrease; dG < 0
Helmholtz free energy (F) decrease; dF < 0
temperature (T) increase; dT > 0
5
A
B
Which statement is CORRECT?
In isolated systems, there can be energy transfer to the environment.
In closed systems, reversible processes increases the entropy.
Everything else, which does not belong to the system is called surroundings
(environment or reservoir).
The intensive quantities are additives.
The dissipative processes are reversible.
1
A
B
C
C
D
E
Solutions: 1A, 2E, 3B, 4A, 5C
12.-13.-14.
1
According to Coulomb’s law,
A
the force between two point charges is proportional to the charge of the
individual point charges, and inversely proportional to the square of the
distance between them.
B
C
the force between two point charges is proportional to the charge of the
individual point charges, and inversely proportional to the distance between
them.
In a closed system, the algebraic sum of electric charges remains constant.
D
the force between two point charges is proportional to the squared charge of
the individual point charges, and inversely proportional to the distance
between them.
E
current intensity is equal to the number of charges transported over unit time.
2
A
B
C
D
E
The electric field within a cavity inside a conducting material...
is zero, according to the Faraday-cage principle.
only depends on the total charges within the cavity, according to Coulomb’s
law.
is infinite.
changes in a harmonic fashion with time.
is circularly symmetric due to the Lorentzian force.
3
A
B
C
D
E
The force acting on a point charge in an electric field is equal to...
the product of the electric field strength and the charge of the point charge.
the ratio of the electric field strength and the charge of the point charge.
the product of the electric flux and the charge of the point charge.
the ratio of the electric flux and the charge of the point charge.
the product of the electric current and the charge of the point charge.
4
A
B
C
D
E
Which statement is FALSE?
Electrostatic field is conservative.
Electrostatic field has no source.
The curl of the electrostatic field is zero.
Electrostatic field is built up by resting charged particles.
In an electrostatic field, Coulomb's law is valid.
5
A
B
C
D
E
For a plate capacitor it is true, that...
their capacitance is proportional to the distance between the plates.
their capacitance is inversely proportional to the area of the plates.
the charge on the plates is proportional to the voltage.
their capacitance is proportional to the square of the distance between the
plates.
their capacitance is inversely proportional to the square root of the area of the
plates.
Solutions: 1A, 2A, 3A, 4B, 5C
1
A
B
C
D
E
What does Ohm’s law state?
R = I/U
The voltage (or potential difference) between two points of a conductor is
proportional to the current that flows through the conductor. The factor of
proportionality is called resistance.
The reciprocal value of resistance is called conductivity.
The number of charges is inversely proportional to the square of the electric
resistance.
The reciprocal value of specific resistance is called specific conductivity.
E
Which statement is CORRECT?
The current intensity is constant in time on each elements of an alternating
current electrical circuit.
The resulting resistance of the resistors in series is the reciprocal value of the sum
of the reciprocals of the individual resistances.
In stacionary current, the sum of the currents flow into the junction equals the
product of the currents flow out of the junction.
The resulting resistance of the resistors in paralel is the reciprocal value of the
sum of the reciprocals of the individual resistances.
In direct current circuit, the sum of the currents flowing into the junction equals the
ratio of the currents flowing out of the junction.
3
Which statement is CORRECT for the induced voltage?
A
The magnitude of the induced voltage is proportional to the rate of magnetic flux.
The magnitude of the induced voltage is inversely proportional to the rate of
magnetic flux.
The magnitude of the induced voltage is independent of the rate of magnetic flux.
The magnitude of the induced voltage only depends on the geometry of the coil.
The magnitude of the induced voltage only depends on the material of the coil
wire.
2
A
B
C
D
B
C
D
E
4
A
B
C
D
E
What effects does NOT electric current have?
heat effect
magnetic effect
chemical effect
light effect
gravitational effect
5
A
Which formula is NOT correct for electric power? (P - power, U - voltage, I current, R - resistance, W - electric work, t - time)
P = U·I
B
P = U2/R
C
D
E
P = I2·R
P = U/I
P = W/t
Solutions: 1B, 2D, 3A, 4E, 5D
2. Signals, signal acquisition and processing
1
A
B
C
D
E
What is NOT deterministic signal?
harmonic
periodic
quasiperiodic
transient
random or stochastic
2
A
B
C
D
E
The steps of signal acquisition and pre-processing:
transducer - amplifier - analog filter - A-D converter - digital processor
transducer - A-D converter - amplifier - analog filter - digital processor
transducer - amplifier - digital processor- analog filter - A-D converter
digital processor - transducer - amplifier - analog filter - A-D converter
amplifier - A-D converter - transducer - analog filter - digital processor
3
A
B
C
D
E
What is the sampling rate required for the proper reconstruction of a signal from its
sample sequence?
at least twice in a period
at least four times in a period
the frequency of the fastest signal component
at least twice the frequency of the fastest signal component
the frequency of the slowest signal component
4
How many voltage levels can be distinguished by an 8-bit analog-digital converter?
A
256 (= 28)
B
8 (= 23)
C
108
D
16 (= 24)
E
32 (=25)
5
A
B
C
D
E
What is the result of high-pass filtering?
the waveform becomes smoother
the rapid changes become milder
the slow fluctuations disappear
the slow and fast changes are both enhanced
the whole waveform is amplified
Solutions: 1E, 2A, 3D, 4A, 5C