Bissoy.com
Doctors Medicines MCQs Q&A

Which of the following methods are used for producing damping torque in analog instruments? 1) Air friction damping 2) Fluid friction damping 3) Eddy current damping 4) Electromagnetic damping

Which of the following methods are used for producing damping torque in analog instruments? 1) Air friction damping 2) Fluid friction damping 3) Eddy current damping 4) Electromagnetic damping Correct Answer 1, 2, 3 and 4

  • Damping System is that part of the instrument which provides damping force to damp the oscillations of the pointer before it comes to rest.
  • Because of inertia, the pointer of the instrument oscillates around its final deflected position for some time before coming to rest.
  • Damping force acts as a brake to prevent these oscillations of the moving system and brings the pointer to it's final deflected position quickly.

 

Methods of damping are:

Air friction 'or' pneumatic damping:

  • In this system, a light aluminum piston is attached to the spindle of the instrument and is arranged to move in a fixed air chamber closed at one end.
  • The compression and suction action of the piston on the air in the chamber damp the possible oscillations of the moving system.

[ alt="F1 S.B 30.5.20 Pallavi D1" src="//storage.googleapis.com/tb-img/production/20/05/F1_S.B_30.5.20_Pallavi_D1.png" style="width: 565px; height: 180px;">

Eddy current damping 'or' Electromagnetic Damping:

  • It is the most efficient type of damping.
  • In this type of damping, a thin disc usually of copper 'or' aluminum is mounted on the spindle. When this disc moves in the magnetic field of the permanent magnet, the line of force are being cut and eddy current is produced.
  • The force that exists between these current and magnetic fields is always in the direction opposing the motion and therefore, provide necessary damping.

[ alt="F1 S.B 30.5.20 Pallavi D2" src="//storage.googleapis.com/tb-img/production/20/05/F1_S.B_30.5.20_Pallavi_D2.png" style="width: 550px; height: 242px;">

Fluid friction damping:

  • In this method of damping, a light disc is attached to the spindle of the moving system and completely submerge in the damping oil in a pot.
  • The motion of the disc is always opposed by a frictional drag on the disc.

[ alt="F1 S.B 30.5.20 Pallavi D3" src="//storage.googleapis.com/tb-img/production/20/05/F1_S.B_30.5.20_Pallavi_D3.png" style="width: 302px; height: 209px;">

Related Questions

Consider the following types of damping: 1. Air-friction damping 2.Fluid-friction damping 3.Eddy-current damping PMMC type instruments use which of the above?
Consider the following statements for deflection and null type instruments: 1. Deflection type of instruments are more accurate than null type of instruments. 2. Deflection type of instruments can be highly sensitive as compared with the null type of instruments. 3. Null type of instruments are more suitable for measurements under dynamic conditions than deflection type of instruments. Which of the above statements are not correct?
Consider the following statements in connection with deflection-type and null-type instruments: 1. Null-type instruments are more accurate than the deflection-type ones. 2. Null-type of instrument can be highly sensitive compared to a deflection-type instrument. 3. Under dynamic conditions, null-type instruments are less preferred to deflection-type instruments. 4. Response is faster in null-type instruments as compared to deflection-type instruments. Which of the above statements are correct?
Which of the following is NOT true about Frictional force? A. Friction is the force which opposes the relative motion of two surfaces in contact. B. The force of friction that acts when a body is moving (sliding) on a surface is called sliding friction. C. Friction in machines wastes energy and also causes wear and tear. D. Rolling friction is much more than sliding friction, the use of ball bearings in a machine considerably reduces friction.
Bernoulli's equation for fluid flow is derived following certain assumptions. Out of the assumptions listed below, which set of assumptions is used in derivation of Bernoulli's equation?
1. Fluid flow is frictionless & irrotational
2. Fluid flow is steady
3. Fluid flow is uniform & turbulent
4. Fluid is compressible
5. Fluid is incompressible
An infinitely long wire carrying a current $$I\left( t \right) = {I_0}\cos \left( {\omega t} \right)$$    is placed at a distance a from a square loop of side a as shown in the figure. If the resistance of the loop is R, then the amplitude of the induced current in the loop is
Electromagnetic Theory mcq question image
Which of the following is not correctly matched? 1. Percussion Instruments: instruments are struck to produce sound. 2. Wind Instruments: need air to flow through them to produce sound. 3. String Instruments: use one or many tightly tied strings that when struck vibrate to create a sound.
The figure shows a constant current source charging a capacitor that is initially uncharged.
Electromagnetic Theory mcq question image
If the switch is closed at t = 0, which of the following plots depicts correctly the output voltage of the circuit as a function of time?
Consider the following statements: 1. The kinetic friction is always less than the rolling friction. 2. The kinetic friction is always equal to the rolling friction. 3. The kinetic friction is always greater than the rolling friction. Which of the following statement is correct?
Which of the following statements regarding static methods are correct?
1. Static methods are difficult to maintain, because you can not change their implementation.
2. Static methods can be called using an object reference to an object of the class in which this method is defined.
3. Static methods are always public, because they are defined at class-level.
4. Static methods do not have direct access to non-static methods which are defined inside the same class.