SAIL ELECTRICAL Questions with answers
1.Two 100-W, 200-V lamps are connected in series across a 200-V supply. The total power consumed by each lamp will be _____ watts.
a)200
b)100
c)50
d)25 –Answer
2.Kirchhoff’s voltage law is not valid for a non-linear network.
a)True
b)False–Answer
3.The material used for fuse must have
a)low melting point and low specific resistance
b)high melting point and low specific resistance
c)low melting point and high specific resistance–Answer
d)none of these
4.If a piece of metal wire is stretched, its resistance will increase.
a)True–Answer
b)False
5.The usual value of the surge impedance of a telephone line is ______ohm.
a)75–Answer
b)600
c)500
d)250
6.In mesh analysis of a network, all the mesh currents must necessarily be either clock-wise or anticlock-wise.
a)True–Answer
b)False
7.The purpose of introducing reactor in the ignition circuit of mercury are rectifier is to limit the
a)voltage of the circuit
b)rate of change of flux in the circuit
c)current in the circuit–Answer
d)rate of change of current in the circuit
8.An uncharged capacitor is connected across a charged one. There will flow an impulsive current through the circuit.
a)True–Answer
b)False
9.In the case of a lossy capacitor, series equivalent resistance value will be
a)small
b)large–Answer
c)very small
d)none of these
10.Time constant of an R-C circuit increases if the value of resistance is
a)decreased
b)increased–Answer
c)neither (a) nor (b)
d)either (a) or (b)
11.If R, L and C denote resistance, inductance and capacitance respectively, the quantity RC has the same dimensions as that of R/L.
a)True
b)False–Answer
12.If R, L and C denote resistance, inductance and capacitance respectively, then the quantity CR2 has the dimensions, of L.
a)True–Answer
b)False
13.Sparking between contacts can be reduced by inserting a
a)capacitor in parallel with contacts–Answer
b)resistance in the line
c)capacitor in series with contacts
d)none of these
14.A battery will not cause any current to flow, when it is connected across a pure capacitor, in the steady state even if the capacitor value varies with time.
a)True
b)False–Answer
15.Voltage stress is maximum in a cable at the surface of the
a)insulator
b)sheath
c)conductor–Answer
d)none of these
16.When two capacitors C1 and C2 are connected in series, the effective capacitance is C1+C2
a)True
b)False–Answer
17.Sparking occurs when a load is switched off because the circuit has high
a)aresistance –Answer
b)inductance
c)capacitance
d)none of these
18.The flux linked with a coil of inductance l carrying a current i is ddt(Li).
a)True
b)False–Answer
19.The coefficient of coupling between two air core coils depends on
a)mutual inductance and self inductances of the two coils–Answer
b)mutual inductance between two coils only
c)self inductances of the two coils only
d)none of these
20. The location of lightning arrestor is
a)away from the transformer
b)near the transformer–Answer
c)near the circuit breaker
d)none of these
21. A conductor of length 1 meter moves at rt. angles to a magnetic field of flux density 1 Wb/m2 with a velocity of 25 m/s. The induced e.m.f. in the conductor will be —– volt.
a)75
b)25–Answer
c)50
d)100
22.In electrical machines, laminated cores are used with a view to reducing
a)eddy current loss–Answer
b)hysteresis loss
23.A battery
a)always delivers power
b)always absorbs power
c)absorbs power when the internal resistance is non-zero but delivers power when the internal resistance is zero
d)can absorb or deliver power depending upon the circuit to which it is connected–Answer
24.When one wants to connect two batteries in parallel to draw larger current than what can be supplied by one battery, it suffices to ensure that their e.m.f.s. are equal.
a)True–Answer
b)False
25.An ideal battery can supply infinite current
a)True
b)False–Answer
26.Decibel is a
a)unit of voltage
b)unit of power
c)ratio of power–Answer
d)none of these
27.dBm is a
a)ratio of power–Answer
b)unit of power
c)unit of voltage
d)none of these
28.Decibel is a unit of
a)frequency
b)impedance
c)power ratio–Answer
d)none of these
29.The absolute unit of resistance is of the dimension of
a)velocity–Answer
b)length
c)acceleration
d)none of these
30.The absolute unit of inductance is of the dimension of
a)time
b)length–Answer
c)mass
d)none of these
31.The applied voltage from the circuit being checked is disconnected when an ohmmeter is used because
a)the current will decrease the resistance
b)the ohmmeter has its own battery
c)no current is needed for meter movements
d)none of these–Answer
32.An accurate voltmeter must have an internal impedance of
a)very high value–Answer
b)very low value
c)low value
d)none of these
33. A moving –coil instrument can be used to measure
a)high frequency a.c.
b)low frequency a.c
c)both d.c. and a.c
d)direct current–Answer
34.The voltage drop across the moving coil of a 50-µ A (f.s) PMMC meter at full- scale deflection is —- the voltage drop across that of a 1-mA (fs) PMMC meter at full-scale deflection.
a)less than
b)approximately equal to–Answer
c)greater than
d)none of these
35.Deflection of pointer of a permanent-magnet moving-coil meter for fixed current is _______ flux density in the airgap between magnetic pole shoes and coil.
a)independent of
b)directly proportional to –Answer
c)inversely proportional to
d)none of these
36. A moving-iron meter is useful for voltage measurement at _______frequencies.
a)high
b)low–Answer
c)very high
d)none of these
37. A thermocouple instruments would be used to measure alternating current only?
a)low
b)very low
c)high –Answer
d)none of these
38.Which of the following instruments will be used to measure alternating current only?
a)moving – iron (attraction-types) ammeter
b)moving – iron voltmeter
c)permanent-magnet type ammeter
d)induction-type ammeter–Answer
39. A milliammeter can be used
a)only as an ammeter
b)as a voltmeter
c)both as voltmeter and ammeter–Answer
d)none of these
40.To measure the e.m.f. of a Weston standard cell, one would use a/an
aelectrostatic voltmeter
b)hot-wire voltmeter
c)galvanometer
d)potentiometer–Answer
41.Deflection sensitivity of deflecting plates of cathode ray tube ____ the distance between deflection pates.
a)is inversely proportional to –Answer
b)is directly proportional to
c)does not depend on
d)none of these
42. Deflection sensitivity of deflecting plates of a cathode ray tube ___the accelerating anode (A3) voltage.
a)is inversely proportional to–Answer
b)is directly proportional to
c)does not depend on
d)none of these
43.A moving – coil instrument can be used to measure
a)direct current –Answer
b)alternating current
c)both direct current and alternating current
d)none of these
44. The frequency stability of a crystal oscillator depends upon
a)tuned circuit
b)crystal–Answer
c)crystal as well as the tuned circuit
d)none of these
45.Hay bridge is usually used for measuring
a)resistance
b)capacitance
c)inductance –Answer
d)none of these
46. Schering bridge is used for measuring
a)capacitance –Answer
b)inductance
c)frequency
d)none of these
47. The Wien’s bridge is particularly useful for measuring frequencies of _______value.
a)low
b)very high
c)high–Answer
d)very low
48. Impedance relay is used to protect
a)line within a particular zone–Answer
b)line beyond a particular zone
c)the whole transmission system
d)none of these
49. Buchholz relay is used in ______ protection.
a)line
b)generator
c)transformer–Answer
d)none of these
50. 1 GHz means 100 Hz.
a)True–Answer
b)False