# MCQs on Control Systems

01․ In the cauer-2 form of LC network---------is series element and --------is shunt element respectively?

In the cauer-2 form of single port LC filter network anlysis C is series element and L is shunt element respectively.

02․ Lowest critical frequency is due to pole and it may be present at the origin or nearer to the origin, then the type of network is

In RC network lowest critical frequency is due to pole and it is at origin or nearer to origin depending on the value of the capacitance value and transfer function.

03․ Lowest critical frequency is due to zero and it may be present at the origin or nearer to the origin, then the type of network is

In RL network lowest critical frequency is due to zero and it is present at origin or nearer to origin as the transfer function has s at the numerator.

04․ Poles and zeros are arranged alternatively on negative real axis, then type of network is/are

In both RC and RL networks poles and zeros are arranged alternatively on negative real axis and in LC network poles and zeros are arranged alternatively on imaginary axis. Zeros occur due to presence of inductance and poles occur due to presence of capacitance respectively.

05․ A box which tells the effect of inputs on control sub system is known as

In a flow chart diagram decision box represents the effects of control sub system. From here the chart will continue to flow to the satisfied condition direction.

06․ Which system is also known as automatic control system?

Control system in which the output has an effect upon the input quantity in order to maintain the desired output value is called closed loop control system. The open loop system can be modified as closed loop system by providing a feedback. The provision of feedback automatically corrects the changes in output due to disturbances. Hence the closed loop control system is also called as automatic control system.

07․ Advantages of open loop system is/are

Advantages of open loop systems:

- The open loop systems are simple and economical
- The open loop systems are easier to construct
- Generally the open loop systems are stable

- Open loop systems are inaccurate and unreliable
- The changes in the output due to external disturbances are not corrected automatically

08․ Which of the following are the disadvantages of a closed loop control system?

Advantages of closed loop control systems:

- The closed loop systems are accurate.
- The closed loop systems are accurate even in the presence of non linearities.
- The sensitivity of the system may be made small to make the system more stable.
- The closed loop systems are less affected by noise.

- The closed loop systems are complex and costly
- The feedback in closed loop systems may lead to oscillatory response
- The feedback reduces the overall gain of the system
- Stability is the major problem in closed loop systems and more care is needed to design stable closed loop systems.

09․ The output of the system has an effect upon the input quantity, then the system is a

Control system in which the output has an effect upon the input quantity in order to maintain the desired output value is called closed loop control system. The open loop system can be modified as closed loop system by providing a feedback. The provision of feedback automatically corrects the changes in output due to disturbances. Hence the closed loop control system is also called as automatic control system.

10․ By using which of the following elements, mechanical translational systems are obtained?

The model of mechanical translational systems can be obtained by using three basic elements mass, spring and dash-pot. These three elements represents three essential phenomena which occur in various ways in mechanical systems.

11․ Force balancing equation of a mass element is (where, x = displacement)

Consider an ideal mass element which has negligible friction and elasticity. Let a force be applied on it. The mass will offer an opposing force which is proportional to acceleration of the body.

12․ Which of the following is/are the advantages of a closed loop control system?

Advantages of closed loop control system:
1. The closed loop systems are accurate
2. The closed loop systems are accurate even in the presence of non linearities
3. The sensitivity of the system may be made small to make the system more stable
4. The closed loop systems are less affected by noise

13․ Force balancing equation of a dash-pot element is (where, x = displacement)

Consider an ideal dash-pot element which has negligible mass and elasticity.
Let a force be applied on it.
The dash-pot will offer an opposing force which is proportional to velocity of the body.

14․ Force balancing equation for elastic element (K) is (where, x = displacement)

Consider an ideal elastic element which has negligible mass and friction. Let a force be applied on it. The elastic element will offer an opposing force which is proportional to displacement of the body.

15․ Which of the following is/are the disadvantages of an open loop control system?

Disadvantages of open loop system:
1. Open loop systems are inaccurate and unreliable.
2. The changes in the output due to external disturbances are not correct automatically.

16․ Which of the following is the analogous quantity for mass element in force-voltage analogy?

The electrical equivalents of the mechanical elements in force-voltage analogy are as follows:
Mechanical element ----------- Electrical analogous element

- Mass element (M) ---------- Inductance (L)
- Spring element (K) --------- Inverse capacitance (1/C)
- Dash-pot (B) -------------- Resistance (R)
- Velocity (v) ----------------- Current (i)
- Displacement (x) ----------- Charge (q)
- Force (f) --------------------- Voltage (V)

17․ Electrical analogous quantity for spring element (K) in force-voltage analogy is

The electrical equivalents of the mechanical elements in force-voltage analogy are as follows:
Mechanical element ----------- Electrical analogous element

- Mass element (M) ---------- Inductance (L)
- Spring element (K) --------- Inverse capacitance (1/C)
- Dash-pot (B) -------------- Resistance (R)
- Velocity (v) ----------------- Current (i)
- Displacement (x) ----------- Charge (q)
- Force (f) --------------------- Voltage (V)

18․ In force-current analogy, electrical analogous quantity for displacement (x) is

The electrical equivalents of the mechanical elements in Force-Current analogy are as follows:
Mechanical element ----------- Electrical analogous element

- Mass element (M) ---------- capacitance (C)
- Spring element (K) --------- Inverse inductance (1/L)
- Dash-pot (B) -------------- Conductance (G=1/R)
- Velocity (v) ----------------- Voltage (V)
- Displacement (x) ----------- Flux (φ)
- Force (f) --------------------- Current (i)

19․ Electrical analogous quantity for dash-pot in force-current analogy is

The electrical equivalents of the mechanical elements in Force-Current analogy are as follows:
Mechanical element ----------- Electrical analogous element

- Mass element (M) ---------- capacitance (C)
- Spring element (K) --------- Inverse inductance (1/L)
- Dash-pot (B) -------------- Conductance (G=1/R)
- Velocity (v) ----------------- Voltage (V)
- Displacement (x) ----------- Flux (φ)
- Force (f) --------------------- Current (i)

20․ If a circuit consists of two mass elements, two spring elements and four friction elements. Find the order of transfer function?

Order of transfer function depends only on mass elements. If a network has "n" number of mass elements, then the order of transfer function is "2×n".
Therefore, from given data, number of mass elements = 2.
Order of transfer function = 2×2 = 4.

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