Sec1-Network Analysis and Syn (Indiabix)

NETWORK ANALYSIS AND SYN SEC1

1. In a parallel resonant circuit, the circuit current at resonance is maximum. A.

True

B.

False

Answer: Option B Explanation:

In parallel resonance current is minimum. View Answer Discuss Answer Discuss in Forum Workspace Report

2. The rms value of wave in figure is

A.

about 95 V

B.

about 80 V

C.

about 50 V

D.

about 25 V


View Answer Discuss Answer Discuss in Forum Workspace Report

3. An RLC series circuit is underdamped. To make it overdamped, the value of R A.

has to be increased

B.

has to be decreased

C.

has to be increased to infinity

D.

has to be reduced to zero

Answer: Option A

Explanation:

For overdamping R is more. View Answer Discuss Answer Discuss in Forum Workspace Report

4. Henry is equivalent to A.

Volts/Ampere

B.

Weber/Volt

C.

Weber/Ampere

D.

Weber/Ampere 2

Answer: Option C Explanation:

Inductance is flux per ampere. View Answer Discuss Answer Discuss in Forum Workspace Report

5. In a minimum function A.

the degree of numerator and denominator are equal

B.

the degree of numerator and denominator are unequal

C.

the degree of numerator is one more than degree of denominator

D.

the degree of numerator is one less than degree of denominator

Answer: Option A Explanation:

If degrees of numerator and denominator were unequal, a pole or zero can be removed. Such a function cannot be a minimum function. Therefore degrees of numerator and denominator must be equal. 6. When a current source I is suddenly connected across a two terminal relaxed RC circuit at time t = = 0, the voltage across the current source is shown in figure. The RC circuit is

A.

a series combination of R and C

B.

a parallel combination of R and C

C.

a series combination of R and parallel combination of R and C

D.

a pure capacitor


Initially capacitor behaves as short-circuit and finally as open circuit. View Answer Discuss in Forum Workspace Report

7. The driving-point impedance Z(s) of a network has a pole-zero locations as shown in the figure. If Z(0) = 3, then Z ( s) is

A.

B.

C.

D. Answer: Option B Explanation:

From figure, The impedance function

and Z(0) =

=3

while in question Z(0) = 3 k = 2.

View Answer Discuss in Forum Workspace Report

8. and i (t ) is a unit step, then V( t ) in the steady state is given by A.

4/9

B.

4/3

C.

0

D.

∞


= 4/9. View Answer Discuss in Forum Workspace Report

9. For a transmission line open circuit and short circuit impedances are 20 Ω and 5 Ω. Then characteristic impedance is A.

100 Ω

B.

50 Ω

C.

25 Ω

D.

10 Ω

Answer: Option D Explanation: Z0 = Zoc Zsc . View Answer Discuss in Forum Workspace Report

10. The terms RMS and average values apply only to sine waves. A.

True

B.

False


These terms are applicable to all waveshapes. 11. The drift velocity of electrons is A.

very small as compared to speed of light

B.

equal to speed of light

C.

almost equal to speed of light

D.

half the speed of light


Drift velocity of electrons is very small. View Answer Discuss in Forum Workspace Report

12. Wave A = 100 sin ωt and wave B = 100 cos ω t . Then A.

rms values of the two waves are equal

B.

rms values of A is more than that of B

C.

rms values of A is less than that of B

D.

rms values of the two waves may or may not be equal


Since peak values are equal, their rms values are equal irrespective of phase difference. View Answer Discuss in Forum Workspace Report

13. Z(c ) for the network shown in the figure is respectively

A.

1/6 F and 4 Ω

B.

2/9 F and 9/2 Ω

C.

2/3 F and 1/2 Ω

D.

1/2 F and 1 Ω

The value of C and R are,

Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Discuss in Forum Workspace Report

14. In an R-C series circuit excited by a voltage E, the charge across capacitor at t = 0+ is A.

0

B.

CE

C.

CE (1 - e-t /RC)

D.

none of the above


Voltage across a capacitor cannot change instantaneously. View Answer Discuss in Forum Workspace Report

15. Two networks are cascaded through an ideal buffer. If t d1 and t d 2 are delay times of network, the overall delay time is A.

t d 1 + t d 2

B.

t 2d 1 + t 2d 2

C.

t d 1 + t d 2

D. Answer: Option C Explanation:

In cascaded networks delay times are added. 16. A series RC circuit has R = 5 Ω and C = 10 μF. The current in the circuit is 5 sin 20000t . The applied voltage is A.

252 sin (20000t + 45°)

B.

252 sin (20000t - 45°)

C.

252 sin 20000t

D.

252 sin (20000t - 90°)


Z = R2 + XC2 = 50 V = 550 sin(20000 t - 45°)

V = 252 sin(20000 t - 45°) View Answer Discuss in Forum Workspace Report

17. A capacitor stores 0.15C at 5 V. Its capacitance is A.

0.75 F

B.

0.75 μF

C.

0.03 F

D.

0.03 μF


Q = CV or 0.15 = C(5) or C = 0.03 F. View Answer Discuss in Forum Workspace Report

18. A 0.5 μF capacitor is connected across a 10 V battery. After a long time, the circuit current and voltage across capacitor will be A.

0.5 A and 0 V

B.

0 A and 10 V

C.

20 A and 5 V

D.

0.05 A and 5 V

Answer: Option B Explanation: When the capacitor is fully charged, i = 0 and voltage across capacitor is equal to battery voltage. View Answer Discuss in Forum Workspace Report

19. For node 1 in figure, KCL equation is

A.

B.

C. D.

none of the above

Answer: Option C Explanation: i (t ) is the incoming current. The currents leaving node 1 are View Answer Discuss in Forum Workspace Report

20. In the circuit of figure, the switch is closed at t = 0. At t = 0+ the current through C is

A.

4A

B.

2.5 A

C.

3.1 A

D.

0

Answer: Option A Explanation: Capacitor behaves as a short-circuit at t = 0. 21. A cable has an insulation resistance of 10 10 ohms. If the length is doubled, the insulation resistance will be A.

2 x 1010 Ω

B.

0.5 x 1010 Ω

C.

1010 Ω

D.

4 x 1010 Ω


Insulation resistance of cable is inversely proportional to length. View Answer Discuss in Forum Workspace Report

22. , i (t ) = A.

3e-4t - e-5t

B.

3e-4t - 2e-3t

C.

2e-4t - 5e-2t

D.

3e-4t - e-t


i (t ) = 3e-4t - 2e-3t View Answer Discuss in Forum Workspace Report

23. In the figure shown, A 1, A2, A3 are identical Ammeters. If A 1 and A3 read 5 and 13 A respectively, reading of A2 will be

A.

8

B.

13 A

C.

18

D.

12 A

Answer: Option D Explanation: A2 = 132 - 25 12 A. View Answer Discuss in Forum Workspace Report

24. Which of the following pairs are correctly matched? Brune's realisation : realisation with ideal transformer. Cauer realisation : ladder realisation. Bott Duffin realisation : with non ideal transformer. Select the answer using the following codes: A.

1, 2 and 3

B.

2 and 3

C.

1 and 3

D.

1 and 2

Answer: Option D Explanation:

Bott Duffins realisation does not use transformer. View Answer Discuss in Forum Workspace Report

25. The synthesis of minimum function was suggested by A.

O'Brune

B.

R. Richards

C.

Bott and Duffin

D.

none of the above


The procedure is called Brune's synthesis. 26. C = (2) (energy)/V 2 A.

True

B.

False



27. A 3 phase balanced supply feeds 3 phase unbalanced load. Power supplied to the load can be measured by using 2 wattmeter one wattmeter 3 wattmeter Which of the above statements is correct? A.

1 and 2

B.

1 and 3

C.

2 and 3

D.

3 alone


A minimum of 2 wattmeters is required to measure 3 phase power. Of course power can be measured by putting one wattmeter in each phase. View Answer Discuss in Forum Workspace Report

28. Which of the following is correct for a driving point functions? A.

The real parts of all poles must be negative

B.

The real parts of all poles and zeros must be negative

C.

The real parts of all poles and zeros must be negative or zero

D.

The real parts of all zeros must be negative


It is a necessary condition for response to be stable. View Answer Discuss in Forum Workspace Report

29. An infinite ladder is constructed with 1 Ω and 2 Ω resistors shown below.

A.

8.18 A

B.

0A

C.

9A

D.

can't determined


R = 1 + (2 || R) R=2 . View Answer Discuss in Forum Workspace Report

30. In the circuit of figure the voltage across capacitor when switch is closed at t = ∞ is

A.

0V

B.

20 V

C.

very large

D.

7.5 V


Voltage across capacitor = voltage across 3Ω resistance = 31. In the series circuit shown in figure, for series resonance, the value of the coupling coefficient, K will be

A.

0.25

B.

0.5

C.

0.1

D.

1

Answer: Option A Explanation: Mutual inductance w m = ωk L1L2 m = k . 2. 8 j 2 = 4k. j Z = 20 - j 10 + j 2 + j 6 + 2.4kj - 2 j + 8kj = 0 at resonance -2 = -8k k = 1/4 0.25 . View Answer Discuss in Forum Workspace Report

32. The degree of the nodes 1, 2, 3, 4 is

A.

2

B.

3

C.

2 for 1, 2, 3, and 3 for 4

D.

all 3


Degree of node is the no.of branch incident to it. View Answer Discuss in Forum Workspace Report

33. In an RC series circuit R = 100 Ω and X C = 10 Ω. In this circuit A.

the current and voltage are in phase

B.

the current leads the voltage by about 6°

C.

the current leads the voltage by about 84°

D.

the current lags the voltage by about 6°


In RC circuit the current leads the voltage. View Answer Discuss in Forum Workspace Report

34. The impedance of an RC series circuit is 12 Ω at f = 50 Hz. At f = 200 Hz, the impedance will be A.

more than 12

B.

less than 3

C.

more than 3 Ω but less than 12 Ω

D.

more than 12 Ω but less than 24 Ω

Answer: Option C Explanation: Z = R2 + XC2. When f is made four times, X C becomes one-fourth but R remains the same. View Answer Discuss in Forum Workspace Report

35. A current is flowing through a conductor with non-uniform area of cross-section. Then A.

current will be different at different cross-sections.

B.

current will be the same at all the cross-sections.

C.

current will be different but current density will be same at all the cross-sections

D.

current will be the same but current density will be different at different cross-sections.


Current density = current/area of cross-section. Same current throughout the conductor. Since, area of cross-section is non-uniform, current density will be different at different crosssections. 36. A series RL circuit has will be A.

. If a voltage 4 sint + 4t is applied, the steady state current

4 sin (4t - 45°)

B.

C.

D. Answer: Option B Explanation: R = 4 Ω, L = 1 H, ω = 4 rad/sec, XL = 4 Ω


37. The electrical energy required to heat a bucket of water to a certain temperature is 2 kWh. If heat losses, are 25%, the energy input is A.

2.67 kWh

B.

3 kWh

C.

2.5 kWh

D.

3.5 kWh


Since 25% of input is lost, 0.75 Input = 2 or input = View Answer Discuss in Forum Workspace Report

38. The circuit in figure will act as ideal current source with respect to terminals A and B when frequency is

A.

0

B.

1 rad/sec

C.

4 rad/sec

D.

16 rad/sec


When ω = 4 rad/sec ωL and

are equal.


39. The current rating of a cable depends on A.

length of cable

B.

diameter of cable

C.

both length and diameter of cable

D.

none of the above


Current rating depends only on area of cross-section and hence diameter. View Answer Discuss in Forum Workspace Report

40. In an ac circuit, the maximum and minimum values of power factor can be A.

2 and 0

B.

1 and 0

C.

0 and -1

D.

1 and -1


Power factor is maximum and equal to 1 for purely resistive load. Power factor is minimum and equal to zero for purely reactive load. 41. The time constant of the circuit in figure shown.

A.

RC

B. C. D. Answer: Option B Explanation: Time constant Req.C when V is shorted and R is seen from C then R eq = R || R = R/2

. View Answer Discuss in Forum Workspace Report

42. In the circuit shown in given figure, the values of i(0 +) and I(∞), will be respectively

A.

zero and 1.5 A

B.

1.5 A and 3 A

C.

3 A and zero

D.

3 A and 1.5 A


I(t ) = 6 e-t - 3 e-0.5t at t = 0, I(0) = 3A at t = ∞, I(∞) = 0. View Answer Discuss in Forum Workspace Report

43. A two branch parallel circuit has a 20 Ω resistance and 1 H inductance in one branch and a 100 μF capacitor in the second branch. It is fed from 100 V ac supply, at resonance, the input impedance of the circuit is A.

500 Ω

B.

50 Ω

C.

20 Ω

D.

5Ω


At parallel resonance circuit impedance =

.


44. The impedance matrices of two, two-port network are given by and . If these two networks are connected in series, the impedance matrix of the resulting two-port network will be

A.

B.

C.

D.

indeterminate


Impedance matrices will be added. View Answer Discuss in Forum Workspace Report

45. As compared to the number of network elements in Brune synthesis, the number of network elements Bott-and Duffin in realization is A.

more

B.

less

C.

equal

D.

any of the above


To avoid mutually coupled inductors, more elements are needed. 46. A sinusoidal voltage has peak to peak value of 100 V. The rms value is A.

50 V

B.

70.7 V

C.

35.35 V

D.

141.41 V


Peak value = 50 V, rms value =

= 35.35 V.


47. A capacitor is needed for an ac circuit of 230 V, 50 Hz the peak voltage rating of the capacitor should be A.

230 V

B.

0.5 x 230 V

C.

2 x 230V

D.

230/2V

Answer: Option C Explanation: Peak voltage rating = 2 (rms voltage rating). View Answer Discuss in Forum Workspace Report

48. The current wave shape shown in figure (1) is applied to a circuit element. The voltage across the element is shown in figure (2). The element is

A.

R

B.

L

C.

C

D.

Semiconductor


When a current pulse is applied to a capacitor the voltage rises linearly and becomes constant at the end of pulse. View Answer Discuss in Forum Workspace Report

49. In figure, the current supplied by battery immediately after switching on the circuit is

A.

1A

B.

4A

C.

10 A

D.

0

Answer: Option A Explanation: At t = 0, inductance behaves as open circuit. View Answer Discuss in Forum Workspace Report

50. RMS value of i (t ) = 10[1 + sin (- t )] is A.

10

B.

10/2

C.

l50

D.

102


.

Sec1-Network Analysis and Syn (Indiabix)

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