1.The current passing through an inductor of resistance 1 ohm and inductance 2 H. The energy absorbed by the inductor in the first four seconds is
(a) 144 J
(b) 98 J
(c) 132 J
(d) 168 J
2. Two infinite strips of width w m in x are carrying
forward and return currents of +I and œI in the z direction. The strips are separated by a distance of xm. The inductance per unit length of the configuration is measured to be L H/m. If the distance of separation between the
strips is now reduced to ,2x m the inductance per unit length of the configuration is
(a) 2L H/m
(b) L/4 H/m
(c) L/2 H/m
(d) 4L H/m
3. A single phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is
(a) 86.7% (b) 88.26% (c) 88.9% (d) 87.8%
4. Group I lists different applications and Group II lists the motors for these applications. Match the application with the most suitable motor and choose the right combination among the choices given thereafter Group I Group II P Food mixer 1 Permanent magnet dc motor
Q Cassette tape recorder 2 Single phase induction motor
R Domestic water pump 3 Universal motor
S Escalator 4 Three phase induction motor
5 DC series motor 6 Stepper motor
(a) P œ 3 Q œ 6 R œ 4 S - 5 (b) P œ 1 Q œ 3 R œ 2 S - 4
(c) P œ 3 Q œ 1 R œ 2 S - 4 (d) P œ 3 Q œ 2 R œ 1 S - 4
5. A stand-alone engine driven Synchronous generator is feeding a partly inductive
load. A capacitor is now connected across the load to completely nullify the
inductive current. For this operating condition.
(a) the field current and fuel input have to be reduced
(b) the field current and fuel input have to be increased
(c) the field current has to be increased and fuel input left unaltered
(d) the field current has to be reduced and fuel input left unaltered
6. Curves X and Y in Fig.Q9 denote open circuit and full-load zero power factor (zpf) characteristics of asynchronous generator. Q is a point on the zpf characteristics
at 1.0 p.u. voltage. The vertical distance PQ in Fig.Q.9 gives the voltage drop across X Voltage (p.u)
(a) Synchronous reactance
(b) Magnetizing reactance
(c) Potier reactance
(d) Leakage reactance
7. No-load test on a 3-phase induction motor was conducted at different supply PY 1.0 Q Field Current
voltages and a plot of input power versus voltage was drawn. This curve was extrapolated to intersect the y-axis. This intersection point yields
(a) Core loss (b) Stator copper loss
(c) Stray load loss (d) Friction and windage loss
8. Bundled conductors are mainly used in high voltage overhead transmission lines to
(a) reduce transmission line losses
(b) increase mechanical strength of the line
(c) reduce corona (d) reduce sag
9. A power system consists of 300 buses out of which 20 buses are generator buses, 25 buses are the ones with reactive power support and 15 buses are the ones with fixed shunt capacitors. All the other buses are load buses. It is
proposed to perform a load flow analysis for the system using Newton-Raphson method. The size of the Newton-Raphson Jacobian matrix is
(a) 553×553 (b) 540×540 (c) 555×555 (d) 554×554
10. Choose two appropriate auxiliary components of a HVDC transmission system from the following
P D.C. line inductor
Q A.C. line inductor
R Reactive power sources
S Distance relays on D.C. line
T Series capacitance of A.C. line
(a) P and Q (b) P and R (c) Q and S (d) S and T
11. A round rotor generator with internal voltage E1 = 2.0 p.u. and X = 1.1 p.u. is
connected to a round rotor synchronous motor with internal voltage E2 = 1.3 p.u.
and X = 1.2 p.u. The reactance of the line connecting the generator to the motor
is 0.5 p.u. when the generator supplies 0.5 p.u. power, the rotor angle difference
between the machines will be
(a) 57.42° (b) 1° (c) 32.58° (d) 122.58°
12. The interrupting time of a circuit breaker is the period between the instant of
(a) initiation of short circuit and the arc extinction on an opening operation
(b) energizing of the trip circuit and the arc extinction on an opening operation
(c) initiation of short circuit and the parting of primary arc contacts
(d) energizing of the trip circuit and the parting of primary arc contacts
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