EE MCQ

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

Related Question

MGVCL Exam Paper (30-07-2021 Shift 1)
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Two-wattmeter method is used to measure the power taken by a 3-phase induction motor on no load. The wattmeter readings are 375 W and –50 W. Calculate the reactive power taken by the load.

Reactive power taken, Q = √3*(W1 - W2)

Q = √3*(375 + 50)

Q = √3*425 kVAR

MGVCL Exam Paper (30-07-2021 Shift 1)
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A 16 A, Type B Miniature Circuit Breaker (MCB) will disconnect a fault in 0.1s when the fault current is

Class B trip curve:

The MCB with class B trip characteristics trips instantaneously when the current flowing through it reaches between 3 to 5 times rated current. These MCBs are suitable for cable protection.

Hence, For 16 A current Type B MCB disconnect fault at 3*16 = 48 A to 5*16 = 80 A.

MGVCL Exam Paper (30-07-2021 Shift 1)
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An RLC series circuit consists of R = 16 Ω, L = 5 mH and C = 2 μF. Calculate the quality factor.

For series RLC circuit,

Q = (1/R)*√(L/C)

Q = 1/16*√(5 mH/2 μF)

Q = 50/16

Q = 3.125