CONTROL SYSTEM - SIGNAL FLOW GRAPH MCQs

This section of Control Systems Multiple Choice Questions and Answers (MCQs) focuses on the ” Signal Flow graph”.It will help you to prepare for various competitive exams.

CONTROL SYSTEM – SIGNAL FLOW GRAPH MCQs

1. The node that has one or more incoming branches only is called as:

A) Source node

B) Sink node

C) output node

D) Both C and D

ANSWER= (D) Both C and D
Explanation:- Sink node or output node: It is a node that has one or more incoming branches only and no outgoing branches.
Source node or input node: It is a node that has only outgoing branches and no incoming branches.

2. Signal flow graph (SFG) is applicable to Nonlinear systems:

A) True

B) False

ANSWER= (B) False
Explanation:- Signal flow graph (SFG) is applicable only to linear time-invariant (LTI) systems.

3. The node having both incoming and outgoing branches is called as:

A) Source node

B) Sink node

C) Chain node

D) Output node

ANSWER= (C) Chain node
Explanation:- Chain node: It is a node that has both incoming and outgoing branches.
Sink node or output node: It is a node that has one or more incoming branches only and has no outgoing branches.
Source node or input node : It is a node that has only outgoing branches and no incoming branches.

4. The transfer function of the signal flow graph given below is :

A) 20

B) 12

C) 16

D) 5

ANSWER= (A) 20
Explanation:- The overall transfer function of SFG is obtained by using Mason’s gain formula.Here in given figure, forward path gain g₁=10 and loop gain L₁=0.5 , Δ₁ =1 and Δ=1-L₁ = 1-0.5 , according to Mason’s gain formula TF = (g₁ .Δ₁)/Δ = 10/1-0.5 =20

5.The combinations of two non touching loops in the given signal flow graph are:

A) 3

B) 4

C) 2

D) 5

ANSWER= (D) 5
Explanation:- There are 5 individual loops in the given SFG. These are L₁= -G₁H₁ , L₂= -G₃H₃. , L₃= -G₁G₂G₃H₂ , L₄= -G₄H₄ , L₅= -G₅H₅ .Also, there are 5 combinations of two non touching loops and these are (i) L₁L₂ (ii) L₁L₅ (iii) L₁.L₄ (iv) L₂L₅. (v) L₃L₅

6.How many forward paths are there in the given signal flow graph?

A) 4

B) 6

C) 5

D) 3

ANSWER= (B) 6
Explanation:- In the given figure there are 6 forward paths i.e g₁.=G₂G₂G₃ , g₂= G₄G₅G₆ , g₃=G₁G₇G₆ g₄=G₄G₈G₃ , g₅= -G₄G₈H₂G₇G₆, g₆=-G₁G₇H₁G₈G₃

7. The number of forward path and individual loops in the signal flow diagram given below are:

A) 3,4

B) 4,2

C) 4,3

D) 2,3

ANSWER= (B) 4,2
Explanation:- It has 4 forward paths g₁= G₁G₂G₇ , g₂=G₄G₇ , g₃=G₁G₆ , g₄=G₄G₃G₆ and has 2 individual loops L₁= G₂G₃ , L₂=G₅.

8. Signal flow graph is used to find:

A) stability of the system

B) Controllability of the system

C) Observability of the system

D) Transfer function of the system

ANSWER= (D) Transfer function of the system
Explanation:-Signal flow graph is used for obtaining the transfer function of the system by using Mason’s gain formula.

9. Which of the following is not a true statement for the signal flow graph?

A) In the signal flow graph signals travel along branches only in the marked direction.

B) Nodes are arranged from right to left in a sequence.

C) Signal flow graphs applicable for the LTI system only.

D) For signal flow, the algebraic equation must be in the form of cause and effect.

ANSWER= (B) Nodes are arranged from right to left in a sequence
Explaination:- In the signal flow graph, nodes are arranged from left to right in a sequence.

10. The number of combination of three non touching loops in the given signal flow graph is: