**1). The transfer function of a real system, H(s), is given as:**

H(s) = As + B/(s^{2} + Cs + D)**, where A, B, Cand D are positive constants. This system cannot operate as**

(a) low pass filter (b) high pass filter (c) band pass filter (d) an integrator

**Answer: (b)**

**Solution:**

With one zero and two poles, the given system cannot be a high pass filter.

**2). For an ideal MOSFET biased in saturation, the magnitude of the small signal current gainfor a common drain amplifier is**

(a) 0 (b) 1 (c) 100 (d) infinite

**Answer: (d)**

**3). The most commonly used relay, for the protection of an alternator against loss of excitation,is**

(a) offset Mho relay (b) over current relay (c) differential relay (d) Buchholz relay

**Answer: (a)**

**Solution:**

Off-set Mho relay protects the generator against loss of excitation

**4). The valid positive, negative and zero sequence impedances (in p.u.), respectively, for a 220kV, fully transposed three-phase transmission line, from the given choices are**

(a) 1.1, 0.15 and 0.08 (b) 0.15, 0.15 and 0.35(c) 0.2, 0.2 and 0.2 (d) 0.1, 0.3 and 0.1

**Answer: (b)**

**Solution:**

For transmission line,

X_{0} = 2.5 to 3 times of X_{1}

**5). A charger supplies 100 W at 20 V for charging the battery of a laptop. The power devices,used in the converter inside the charger, operate at a switching frequency of 200 kHz. Whichpower device is best suited for this purpose?**

(a) IGBT (b) Thyristor (c) MOSFET (d) BJT

**Answer: (c)**

**Solution:**

For higher switching frequencies like 200 kHz, power MOSFET is best suitable.

**6). The type of single-phase induction motor, expected to have the maximum power factorduring steady state running condition, is**

(a) split phase (resistance start) (b) shaded pole(c) capacitor start (d) capacitor start, capacitor run

**Answer: (d)**

**Solution:**

Having a run capacitor [permanent capacitor] can improve the power factor of induction motor

**7). A MOD 2 and a MOD 5 up-counter when cascaded together resuls in a MOD _____ counter.(in integer)**

**Answer: (10)**

**Solution:**

Modulus of a cascaded counter of Mod-M and Mod-N is MN

Hence, modulus of a cascade of Mod-2 and Mod-5 counter = 5 X 2 = 10

**8). The frequencies of the stator and rotor currents flowing in a three-phase 8-pole inductionmotor are 40 Hz and 1 Hz, respectively. The motor speed, in rpm, is _____ (round off tonearest integer)**

**Answer: (585)**

**Solution:**

S = 1/40

Rotor speed

N_{r} = (1-1/4) (120 x 40/8) = 585 rpm

**9).** **A 3-phase, 415 V****, 4-pole, 50 Hz** **induction motor draws** **5 times the rated current at** **rated****voltage at starting. It is required to bring down the starting current from the supply to 2times of the rated current using a 3-phase autotransformer. If the magnetizing impedanceof the induction motor and no-load current of the autotransformer is neglected, then thetransformation ratio of the autotransformer is given by _______ (round off to two decimalplaces).**

**Answer: (0.6324)**

**Solution:**

When auto-transformer starter is used,

x = 0.6324

**10). Consider a 3** x **3 matrix A whose (i, j)-th element, a** **i,j = (i – j)** ^{3}**. Then the matrix A will be**

(a) symmetric (b) skew-symmetric (c) unitary (d) null

**Answer: (b)**