Quiz 2 MEC522/MEM686 SEM2 2022/23

First order system is defined as : [CO1/PO1]

• Number of poles at origin
  

• Order of the differential equation
  

• Total number of poles of equation

• Total number of poles and order of equation

Answer explanation

First order system is defined by total number of poles and also which is same as the order of differential equation.

Time response during steady state the output velocity matches with the input velocity but lags behind the input by T. [CO1/PO1]

• True

• False

Answer explanation

In first order systems the time response during steady state the output velocity matches with input velocity but lags behind the input by T.

The system in originally critically damped if the gain is doubled the system will be :
[CO1/PO1]

• Remains same

• Overdamped

• Under damped

• Undamped

The damping ratio and peak overshoot are measures of:
[CO1/PO1]

• Relative stability

• Steady state error

• Speed of response

• Absolute stability

Answer explanation

Speed of response is the speed at which the response takes the final value and this is determined by damping factor which reduces the oscillations and peak overshoot as the peak is less then the speed of response will be more.

• 0

• infinity

• 1/15

• 1/14

The steady state error of a stable 'type 1' unity feedback system for a unit step function is equal to: ______ [CO1/PO1]

• infinite

• 0

• 1/Kv

• finite

For a stable closed loop system, the gain at phase crossover frequency should always be: ______ [CO1/PO1]

• < 20 dB
  

• < 6 dB

• > 6 dB

• > 0 dB

Answer explanation

Phase crossover frequency is the frequency at which the gain of the system must be 1 and for a stable system the gain is decibels must be 0 db.

If the gain of the open loop system is doubled, the gain of the system is : [CO1/PO1]

• Not affected

• Doubled

• Halved

• One fourth of the original value

Answer explanation

Gain of the open loop system is doubled then the gain of the system is not affected as the gain of the system is not dependent on the overall gain of the system.

If the Nyquist plot of the open loop transfer function G(s)H(s) of a system passes through -1 + j0 point, then the phase margin of the system is likely to be ____ [CO1/PO1]

• 45 degrees

• 180 degrees

• 0 degree

• 90 degrees

In a bode magnitude plot, which one of the following slopes would be exhibited at high frequencies by a 4th order all-pole system?
[CO1/PO1]

• -80dB/decade

• -40 dB/decade

• 40 dB/decade

• 80 dB/decade

Answer explanation

A 4th order all pole system means that the system must be having no zero or s-term in numerator and s⁴ terms in denominator. One pole exhibits -20dB/decade slope, so 4 pole exhibits a slope of -80 dB /decade.