If the star side of the star-delta transformer shown in the figure is excited by a negative sequence voltage, then

**A. ** V_{AB} leads Vab by 60º

**B. ** V_{AB} lags Vab by 60º

**C. ** V_{AB} leads Vab by 30º

**D. ** V_{AB} lags V_{ab} by 30º

**Answer : ****Option D**

**Explaination / Solution: **

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In a constant V/f induction motor drive, the slip at the maximum torque

**A. ** is directly proportional to the synchronous speed.

**B. ** remains constant with respect to the synchronous speed.

**C. ** has an inverse relation with the synchronous speed.

**D. ** has no relation with the synchronous speed.

**Answer : ****Option C**

**Explaination / Solution: **

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Consider a system consisting of a synchronous generator working at a lagging power factor, a synchronous motor working at an overexcited condition and a directly grid-connected induction generator. Consider capacitive VAr to be a source and inductive VAr to be a sink of reactive power. Which one of the following statements is TRUE?

**A. ** Synchronous motor and synchronous generator are sources and induction generator is a sink of reactive power.

**B. ** Synchronous motor and induction generator are sources and synchronous generator is a sink of reactive power.

**C. ** Synchronous motor is a source and induction generator and synchronous generator are sinks of reactive power.

**D. ** All are sources of reactive power.

**Answer : ****Option A**

**Explaination / Solution: **

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A 4-pole, lap-connected, separately excited dc motor is drawing a steady current of 40 A while running at 600 rpm. A good approximation for the waveshape of the current in an armature conductor of the motor is given by

**A. **

**B. **

**C. **

**D. **

**Answer : ****Option C**

**Explaination / Solution: **

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If an ideal transformer has an inductive load element at port 2 as shown in the figure below, the equivalent inductance at port 1 is

**A. ** nL

**B. ** n^{2}L
**C. ** n/L

**D. ** n^{2}/L
**Answer : ****Option B**

**Explaination / Solution: **

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A function y(t), such that y(0) = 1 and y(1) = 3e^{-1}, is a solution of the differential equation Then y(2) is

**A. ** 5e-1

**B. ** 5e-2

**C. ** 7e-1

**D. ** 7e-2

**Answer : ****Option B**

**Explaination / Solution: **

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The value of the integral

**A. **

**B. **

**C. ** 24/13

**D. ** 12/13

**Answer : ****Option B**

**Explaination / Solution: **

over the contour |z| = 1, taken in the anti-clockwise direction, would be

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Consider a continuous-time system with input x(t) and output y(t) given by
y(t) = x(t) cos(t)
This system is

**A. ** linear and time-invariant

**B. ** non-linear and time-invariant

**C. ** linear and time-varying

**D. ** non-linear and time-varying

**Answer : ****Option C**

**Explaination / Solution: **

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Suppose x_{1}(t) and x_{2}(t) have the Fourier transforms as shown below

**A. ** x1(t) and x2(t) are complex and x1(t) x2(t) is also complex with nonzero imaginary part

**B. ** x1(t) and x2(t) are real and x1(t) x2(t) is also real

**C. ** x1(t) and x2(t) are complex but x1(t) x2(t) is real

**D. ** x1(t) and x2(t) are imaginary but x1(t) x2(t) is real

**Answer : ****Option C**

**Explaination / Solution: **

Which one of the following statements is TRUE?

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The output of a continuous-time, linear time-invariant system is denoted by T{x(t)} where x(t) is
the input signal. A signal z(t) is called eigen-signal of the system T , when T{z(t)} = γz(t),
where γ is a complex number, in general, and is called an eigenvalue of T. Suppose the impulse
response of the system T is real and even. Which of the following statements is TRUE?

**A. ** cos(t) is an eigen-signal but sin(t) is not

**B. ** cos(t) and sin(t) are both eigen-signals but with different eigenvalues

**C. ** sin(t) is an eigen-signal but cos(t) is not

**D. ** cos(t) and sin(t) are both eigen-signals with identical eigenvalues

**Answer : ****Option D**

**Explaination / Solution: **

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