141.  The function G(s) H(s) of a system has no poles in the RHS of s-plane. For the system to be stable, the Nyquist plot of G(s) must not enclose the
A. origin
B. point (? 1, j0)
C. point (? 1, ? jl)
D. point (1, j0)

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142.  On adding a pole at s = 0, the Nyquist plot of a system will
A. remain unaltered
B. rotate clockwise by 90?
C. rotate anticlockwise by 90?
D. rotate by 180

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143.  Polar plots for positive and negative frequencies
A. are always symmetrical
B. can never be symmetrical
C. may or may not be symmetrical
D. none of these

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144.  The actuating signal in a control system is always fed to
A. the controlled element
B. the feedback element
C. the control element
D. all of these

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145. In a control system, the controller consists of
A. error detector
B. error detector and control element
C. error detector and controlled element
D. none of these

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146. The Op Amp control components in a control system ideally draw
A. medium current
B. small current
C. very small current
D. zero current

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147.  Which of the following system provides good performance if offset is to be avoided?
A. proportional action
B. proportional plus integral action
C. proportional plus differential action
D. proportional plus integral action plus differential action

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