Network Theory Mid - I, February - 2012

1.The direction of rotation of a three phase induction motor is clockwise when it is supplied with 3ph sinusoidal voltage having phase sequence ABC. For counter clockwise rotation of the motor, the phase sequence of the power supply should be
  • BCA
  • CAB
  • ACB
  • BCA or CAB
Answer: C
2.The rated voltage of a 3phase power system in general is given as
  • rms phase voltage
  • peak phase voltage
  • peak line to line voltage
  • rms line to line voltage
Answer: D
3.Total instantaneous power supplied by a 3ph ac supply to a balanced RL load is
  • zero
  • constant
  • pulsasting with zero average
  • pulsating with non-zero average
Answer: B
4.At steady state the inductor acts as a
  • SC
  • OC
  • resistor
  • transistor
Answer: A
5.A RC series circuit has R=2ohms and C=4F. The time constant is ___sec.
  • 0.5
  • 2
  • 4
  • 8
Answer: D
6.Laplace transform analysis gives
  • time domain response
  • frequency domain response
  • both a and b
  • none
Answer: B
7.The final value of the function 6-6e- t is
  • 1
  • 3
  • 6
  • -6
Answer: D
8.The inverse laplace of the function 1/(e-a)
  • e
  • e^-t
  • e^at
  • e^-at
Answer: C
9.The reciprocal of driving point admittance is
  • driving point impedance
  • resistance
  • inductance
  • both b and c
Answer: A
10.The ratio of voltage transform at one port to the current transform at the other port is called [ ] ______________ transform
  • voltage
  • current
  • impedance
  • admittance
Answer: C
11.Power factor of an unbalanced system is given by the expression _____________.
Answer: -
12.If Vab=400∟0 volts in a balanced star connected 3phase generator find the phase voltages, assuming the phase sequence acb are ________, ____________, _____________.
Answer: Va=230.94∟30, Vb=230.94∟150, Vc=230.94∟270
13.At t=0 a initially charged capacitor behaves as a ________________.
Answer: voltage source
14.A voltage v(t)=12t2 is applied across a 1H inductor for t0, with initial current through it being 0. The current through the inductor for t>=0 is given by__________.
Answer: 4t^3
15.The condition for a second order RLC series circuit to be critically damped is __________.
Answer: (R/2L)^2 = 1/LC
16.The initial value of the function 2-e5t is ________.
Answer: 1
17.The inverse laplace transform of the function 1/(s2(s 1)) is _____________.
Answer: t+e^(-t)-1
18.The transform inductance for inductor is given as _________.
Answer: sL
19.The ratio of voltage transform at one port to the voltage transform at the other port is called ______________________.
Answer: voltage transform ratio
20.At poles the network function becomes ____________.
Answer: infinite