EE MCQ

MGVCL Exam Paper (30-07-2021 Shift 1)
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A thermistor is inherently suitable for temperature measurement involving

Thermistors are ideal when measuring a single point temperature that is within 50°C of ambient.

If the temperatures are excessively high or low, a thermistor will not work.

Most thermistors work best in the range between -55°C and +114°C.

Sensitivity of thermistor is high.

Span value of thermistor is low.

Related Question

MGVCL Exam Paper (30-07-2021 Shift 1)
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An eight-pole wave-connected armature has 600 conductors and is driven at 625 rev/min. If the flux per pole is 20 mWb, determine the generated emf.

Let,

E→EMF in volt

φ→Flux in weber

A→Parallel path (for wave winding = 2)

Z→No. of armature conductors

N→speed in rpm

P = Number of poles

E = PφNZ/(60A)

E = 8*0.020*625/(60*2)

E = 500 V

MGVCL Exam Paper (30-07-2021 Shift 1)
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A coil having an inductance of 100 mH is magnetically coupled to another coil having an inductance of 900 mH. The coefficient of coupling between the coils is 0.45. Calculate the equivalent inductance if the two coils are connected in series aiding.

Mutual inductance (M) = k*√(L1*L2)

k = 0.45

M = 0.45*√(900*100*10⁻⁶) = 135 mH

Leq = L1 + L2 + 2M

Leq = 900 + 100 + 270

Leq = 1270 mH

MGVCL Exam Paper (30-07-2021 Shift 1)
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Three equal star-connected inductors take 8 kW at 0.8 power factor when connected to a 460 V three - phase 3-wire supply. If one of the inductor in phase – Y is short circuited, then the line current in phase-Y is ___ Assume RYB sequence.

Here, Y phase is shorted,

Equation of 3-phase power = √3*VL*IL*cosφ

IL = P/(√3*VL*cosφ)

= 8000/(√3*400*0.8)

= 12.55 A

Phase impedance = Vp/Ip

= 460/(√3*12.55)

= 21.16 ohm

cosφ = 0.8, So φ = 37 degree.

Here Impedance of Y phase is shorted,

So, Neutral point and Y phase at same potential,

Three line voltages are given by,

Vry = 460∟0°

Vyb = 460∟120°

Vbr = 460∟-120°

Here N and Y phase at same potential,

Ir = (460∟-120°)/(21.16∟37°)

= -21.7∟83° A

Ib = (-460∟120°)/(21.16∟37°)

= 21.7∟-157° A

Ib = -(Ir + Iy)

= -21.7∟83° + 21.7∟-157°

= 37.6∟53° A