Test 1
1. The instantaneuos voltage across an ideal inductance is:
a) uL=Li, b) u L 
1
di
di
idt , c) u L  L , d) u L  R , e) u L  Li

L
dt
dt
2. The measuring unit for the active power is: a) VA, b) W, c) VAR, d) WA, e) without
3. In order to solve a circuit using the Thevenin’s theorem one need to know: a) the shortcircuit voltage, b) the short-circuit current, c) the open-circuit voltage, d) the zero-input
and zero-state equivalent network impedance, e) the equivalent impedance of the circuit.
4. From the derivation of a sinusoidal time function result: a) a non-sinusoidal waveform, b)a
counter-clockwise rotation of the phasor with /2, c) a counter-clockwise rotation of the
phasor with , d) a clockwise rotation of the phasor with /2, e) the effective value is 
times smaller
5. The average value of a sinusoidal quantity over a period is:
a) 2/Im b) any value, c) zero,
d) /2
e) I 2
6. The series impedance connection could be used as: a) voltage and current devider,
b)voltage devider, c) current devider, d) current multiplicator, e) voltage multiplicator
7. The integration of a sinusoidal current has as result:
a) a non-sinusoidal wave-form, b) a counter-clockwise rotation of the phasor with , c)a
sinusoidal current rotated clockwise with /2, d)a counter-clockwise rotation of the phasor
with /2, e) the amplitude is devided by 
8. The following phasor U  j X I is: a) in phase with I , b) leads the initial phasor with
/2, c) lags behind the initial phasor by /2 faţă de I , d) in antiphase, e) any value
9. For a series circuit we have to consider as reference: a) the current, b) the voltage, c) the
voltage or the current, d) the instantaneous power, e) resistance
10. The relation
 1

R 2  
  L 

C


2
represents: a) the impedance of a parallel circuit, b) the
impedance of some circuit, c) the impedance of a series circuit, d) the admitance of a
series circuit, e) the admitance of a parallel circuit
11. The instantaneuos voltage across an ideal capacitor is:
a) uC =Ci, b) u C 
1
di
1
idt , c) u C  C , d) uC  Ci , e) u C 
i

C
dt
C
12. The equivalent inductance can be:
a) positive or negative, b) only negative, c) only positive, d) zero, e) in phase
13. The following expression
1
  L represents: a) resonance condition for a series circuit
C
only, b) resonance condition for a parallel circuit only, c) resonance condition for series
and parallel circuits, d) it is not a resonance condition, e) it is the equivalent impedance
14. An odd function has a Fourier series consisting:
a) only of sine terms, b) only of cosine terms, c) a constant component and cosine terms,
d)a constant component and sine terms, e) a constant component
15. For two-port networks, the relation A  D represents:
a) symmetry condition, b) is valid no matter of the type of circuit, c) reciprocity condition,
d) the set-up condition for a two-port network, e) a relation between impedance parameters
Test 1
a) U ef  2U ,
16. The effective (r.m.s.) value of a non-sinusoidal function is:
T
1 2
u t dt , d) U  U 02  U12  U 22   , e) U  U 12  U 22  

T0
b) U max  2U , c) U 
17. For two-port networks, the relation AD  BC  1 represents:
a) symmetry condition, b) is valid no matter of the type of circuit, c) reciprocity condition,
d) the set-up condition for a two-port network, e) a relation between impedance parameters
18. In a circuit driven by a non-sinusoidal voltage:
a)the capacitor worses the waveform, b) the capacitor improves the waveform, c) the
current waveform is not affected, d) there is no phase shift, e) the resistance worses the
waveform
19. The instantaneous power: a) the measuring unit is watt, b) it is a sinusoidal quantity, c) it is
a constant, d) it cannot measured, e) it is a non-sinusoidal quantity


20. The complex representation of it   2 sin 250t  60 o is:
b) I  2e  j 60 , c) I 
o
2
2
e j  3 , d) I  2 2e j 250t , e) it  
a) it   2e j 250t   3 ,
2
0
e 60
2
21. The active power transfer: a) it takes place in pure resistive circuits, b) it has a maximum
value when the phase shift between the currents is /2, c) it has a maximum value when the
currents are in phase, d) it takes place in inductively coupled circuits, e)there is no such
transfer
22. In order to match a load to a source we need to use: a) the open circuit impedance, b)image
impedances, c) the characteristic (iterative) impedance, d) the short-circuit impedance,
e)the series impedance
23. The real capacitor: a) there is no active power loss in a.c., b) there is active power loss in
a.c., c) the phase shift between the current and the voltage is 900, d) the phase shift between
the current and the voltage is smaller than 900, e) the phase shift between the current and
the voltage is greater than 900
24. The wave amplitude compared to the complex spectral amplitude is: a) two times smaller,
b) two times greater, c) equal, d) there is no relation between them, e) can have any value
25. The derivation of sinusoidal time function corresponds to: a) the division of the
corresponding complex quantity by j, b)the multiplication of the corresponding complex
quantity by j, c) the addition of the complex images, d) the multiplication by the phase of
the sine quantity, e) simplification by e jt
26. In a circuit driven by a non-sinusoidal voltage:
a)the inductor worses the waveform, b) the inductor improves the waveform, c) the current
waveform is not affected, d) there is no phase shift, e) the resistance worses the waveform
27. For the complex impedance: a) the modulus equals the impedance of the circuit, b) the
argument is the phase shift between the voltage and the current taken with negative sign,
c)the real part is the conductance of the circuit, d) the imaginary part is known as the
reactance of the circuit, e) the imaginary part is zero
28. The instantaneous value of I  2 j is:
c) it   2 2 cos t ,
b) it   2e j t   ,
a) it   2 sin t ,
d) it   2 2 sin t   2 ,
e) it  
2
2
sin t   2
Test 1
29. The characteristic (iterative) impedance of a symmetrical two-port network is:
a)  0 
1
LC
, b) L 
1
B
AB
DB
, c) Z c  
, d) Z i1  
, e) Z i 2  
C
C
CA
CD
30. The energy losses in the dielectric (capacitor) are caused by: a) the amplitude permitivity,
b) the elastic permitivity, c) the viscous permitivity, d) the inductance of dielectric, e) the
complex permeability
31. The following equations U 1  AU 2  BI 2 , I 1  CU 2  DI 2 are called: a) the fundamental
equations of the air core transformer, b) transmission line equations, c) there is no
practical significance, d) fundamental equations of the two-port networks, e) Z parameters
equations
32. Parallel resonance: a) the current is maximum, b) it is called voltage resonance too, c) it
may occur over-currents, d) the voltages over the capacitor and inductor are different,
e)the resonance condition for series and parallel circuits are different
33. Vaschy’s theorem: a) it is applied to branches connected to a node, b) it is applied to
loops, c) it is referred to current real sources, d) it is referred to real voltage sources, e) it
is applied to magnetically coupled circuits
34.     j is the complex propagation constant: a) it is calculated as the ratio of the input
and output voltages, b)  is called propagation constant, c)  is called phase constant, d) if
<0 the signal is amplified, e) if 0 the signal is attenuated
35. The node voltages method: a) it is applied to the loops of a circuit, b) the unknown
quantities are the loop currents, c) the self-admittance of a node is the sum of the
impedances connected to the node, d) the short-circuit current is calculated using the
Kirchhoff’s current law, e) the self-admittance of a node is the sum of the admittances of all
branches connected to the node
36. Series resonance: a) the current value is determined only by the resistance, b) it is called
current resonance too, c) it may occur over-currents, d) the current has a maximum value,
e) the voltages over the capacitor and inductor are different
37. In a symmetrical three-phase system: a) the phase-shift between the phasors is /6, b) the
phasors rotation is in a clockwise direction, c) the sum of the phasors equals the sum of the
corresponding modules, d) the vector diagram is a symmetric star, e) there are different
phase shift between the phasors
38. The even function has a Fourier series consisting: a) only of sine terms, b) only of cosine
terms, c) a constant component and cosine terms, d) a constant component and sine terms,
e) a constant component
39. In three-phase circuits, for delta (or mesh) connection:
a) I l  I f , b) I l  2I f , c) I l  3I f , d) I f  3I l , e) U f  U l
40. The sentence “the input and the output can be interchanged without altering the response of
the system to a given input waveform” represents: a) the superposition theorem, b) the
reciprocity theorem, c )the Thevenin theorem, d) the Norton theorem, e) the practical
application of the loop analysis of a linear network