274. The loop gain GH of a closed loop system is given by the following expression s(s + 2) (s + 4) The value of K for which the system just becomes unstable is

A. K = 6

B. K = 8

C. K = 48

D. K = 96

275. For a given stepper motor, the following torque has the highest numerical value.

A. Detent torque

B. Pull-in torque

C. Pull-out torque

D. Holding torque

276. The following motor definitely has a permanent magnet rotor

A. DC commutator motor

B. Brushless dc motor

C. Stepper motor

D. Reluctance motor

277. For a tachometer if 0(t) is the rotor displacement is radians, e(t) is the output voltage and Kt is the tachometer constant in V/rad/sec, then the transfer E(s)function, will be 0(s)K,

A. Kts2

B.

C. Ks

D. Kt

278. A unity feedback system, having an open loop gain G(s) H(s) - K(1 - s) , becomes (1 + s) stable when

A. IKI > 1

B. K > 1

C. IKI < 1

D. K < -1

279. In the GH(s) plane, the Nyquist plot of the loop transfer function G(s)H(s) passes through the negative real axis at the point

A. (-0.25, j0)

B. (-0.5, j0)

C. (-1, j0)

D. (-2, j0)

280. The response of a system by -T + i =v. dtli the excitation is v = ke2t, then the forced response of i for t> 0 will be HAS 20001 k,

A. ?3 e'

B. 5? e-t

C. ?5 e-

D. ? sint + ?5 cost

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