Test: Modelling of Control Systems- 2 - Electronics and Communication Engineering (ECE) MCQ

let's analyze the characteristics of each type of friction:

1. Static friction (A) - This type of friction occurs when there is no relative motion between the surfaces in contact. The frictional force increases up to a maximum value as the applied force increases, and it equals the applied force until motion starts. After this point, it transitions to kinetic friction. This corresponds to a frictional force that stays at zero until the velocity starts changing.
2. Coulomb friction (B) - Also known as kinetic or dry friction, this type of friction remains constant regardless of the velocity once the object is in motion. It is independent of the velocity of the moving surfaces. This corresponds to a horizontal line for the frictional force versus velocity curve.
3. Viscous friction (C) - This type of friction is proportional to the velocity. The frictional force increases linearly with the velocity. This corresponds to a linear relationship between frictional force and velocity.

Now, match these characteristics with the curves in List-II:

• Curve 1 shows a frictional force that increases linearly with velocity. This corresponds to Viscous friction.
• Curve 2 shows a constant frictional force regardless of the velocity. This corresponds to Coulomb friction.
• Curve 3 shows a frictional force that is zero until a certain point (indicating no movement) and then jumps to a certain value once motion starts. This corresponds to Static friction.

So, the correct matching is:

• A: 3 (Static friction)
• B: 2 (Coulomb friction)
• C: 1 (Viscous friction)

The correct answer is (d): 3 2 1

Both assertion and reason are true. However, the correct reason is that all the forces in the direction of reference direction are considered as positive and the forces opposite to the reference direction are taken as negative due to which the algebraic sum of forces is zero.

When two time constant elements are cascaded non-interactively, then the overall transfer function is the product of two individual TFs.
Hence, assertion is false.

Reason is a false statement because small diameter and large axial length will give a lower value of inertia of motor.

Stepper motors can be used for speed control because the motor speed is proportional to the rate of command pulses.

and 

If q = flow; A = Area of cross-section and h = height of water in tank.

On comparing equations (i) and (ii), we have C (Farad) = A = m²