This Portion of Electrical andElectronic Measurements and Measuring instruments contains Galvanometers MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.

**This Section covers below lists of topics.**

- D’Arsonval Galvanometer
- Construction of D’Arsonval Galvanometer
- Dynamic behavior of Galvanometer
- Response of Galvanometer
- Operational Constants
- Relative Damping
- Logarithmic Decrement
- Overshoot
- Damping
- Sensitivity
- Galvanometer Shunts
- Ballistic Galvanometer
- Flux Meter
- Vibration Galvanometer

#### 1. In d’Arsonval galvanometer, an iron core is usually used between the permanent magnet pole faces. This is used so that

- Flux density in the air gap becomes high therby a large deflecting torque is produced
- The effect of stray magnetic fields is reduced
- Moment of inertia of moving parts becomes smaller.
- None of the above.

A. Flux density in the air gap becomes high therby a large deflecting torque is produced

#### 2. Sometimes, d’Arsonval galvanometers, do not use ferromagnetic cores between poles of the permanent magnet. In this case

- The flux density becomes smaller resulting in low deflecting torque
- The dimension of moving coil can be made smaller thereby reducing the moment of inertia
- The magnetic field may not be radial resulting in a non-uniform scale even if spring control is used
- All the above

D. All the above

#### 3. A d’Arsonval galvanometer uses a light and scale arrangement. The light source is placed 1 m away from the moving system of galvanometer. The arrangement uses a circular scale calibrated in mm. the deflection indicated by the scale is

- 1000mm
- 2000mm
- 500mm
- None of the above

B. 2000mm

#### 4. if a current of 1 µ A is passed through the coil. The spring stiffness is 2 × 10^{-6} Nm/rad and the displacement constant is 2 Nm/A. the time period of free oscillations in a galvanometer having a relative damping of 0.6 is 2 s. the frequency of damped oscillation is :

- 0.5 rad/s
- 0.3 rad/s
- 0.4 rad/s
- None of the above

C. 0.4 rad/s

#### 5. The relative damping in a galvanometer is 0.8 its logarithmic decrement is approximately

- 0.48
- 1.25
- 4.19
- -4.19

C. 4.19

#### 6. In a critically damped galvanometer the deflection at a time 0.9 times the time of free oscillations after a current is passed through the moving coil is approximately

- 0.986 times the final deflection
- 0.901 times the final deflection
- 0.866 times the final deflection
- None of the above.

A. 0.986 times the final deflection

#### 7. The resistance required for critical damping in a circuit is 1000Ω. The galvanometer circuit has a resistance of 800 Ω. Is the galvanometer circuit :

- Underdamped
- Undamped
- Overdamped
- None of the above

C. Overdamped

#### 8. A galvanometer has a ratio of 0.9 for damped frequency oscillations to undamped frequency of oscillations. Suppose moment of inertia, stiffness constant and damping constant is made twice their original value that would be the new ratio of damped frequency oscillations to undamped frequency oscillations.

- 0.9
- 1.11
- 4
- 2

A. 0.9

#### 9. A circuit of 2 µ A is passed through the moving coil of an undamped d’Arsonval galvanometer which has a displacement constant of 2 Nm/A and a control constant of 10 ×10^{-6 }Nm/rad. The moving oscillates with an amplitude of :

- 0.2 rad
- 0.4 rad
- 0.8 rad
- None of the above.

C. 0.8 rad

#### 10. If the damping in the d’Arsonval galvanometer is only due to electromagnetic effects,the resistance required for critical damping is _________
Where G = displacement constant ; Nm/A, K = control constant ; Nm/rad and J = inertia constant ; kg-m^{2}.

- G
^{2}/ √KJ - G / √KJ
- G / 2√KJ
- G
^{2}/ 2√KJ

D. G

^{2}/ 2√KJ#### 11. A d’arsonval galvanometer uses a lamp and scale arrangement. Its current sensitivity is 250 mm/µ if the resistance of the coil is 100 Ω. And the external resistance required for critical damping is 900 Ω (which is connected in the circuit), the voltage sensitivity is

- 0.25 mm/µV
- 0.25 mm/V
- 2.5 mm/ µV
- 250 mm/ µV

A. 0.25 mm/µV

#### 12. Ayrton shunt is used in d’Arsonval galvanometers so as to limit the current in the galvanometer coil to its maximum permissible value. The relative value of current through the galvanometer coil and the shunt

- Depends upon the value of resistance of galvanometer coil only
- Depends upon the resistance of galvanometer coil and the shunt
- Does not depends upon the value of resistance of galvanometer coil
- None of the above.

C. Does not depends upon the value of resistance of galvanometer coil

#### 13. A ballistic galvanometer should be designed with

- Large period of natural oscillations and a negligible damping constant
- A small period of natural oscillations and high damping constant
- A large period of natural oscillations and a high damping factor
- Small period of natural oscillations and a low damping factor.

A. Large period of natural oscillations and a negligible damping constant

#### 14. In a flux meter

- The controlling torque is produced by weights attached to moving coil
- The controlling torque is produced by springs
- There is no controlling torque
- None of the above.

C. There is no controlling torque

#### 15. In an unshunted flux meter,the sensitivity is dependent upon

- resistance of moving coil
- resistance of search coil
- resistance of both search and moving coil
- none of the above.

D. none of the above.

#### 16. A vibration galvanometer is to be turned to a frequency of 50 Hz. The ratio of its control constant to inertia constant should be

- 98696
- 2500
- 132 × 10
^{-6} - None of the above.

A. 98696

#### 17. A vibration galvanometer is tuned

- By changing the length and tension of vibrating coil
- By attaching weights to vibrating coil
- By changing its damping constant
- All the above.

A. By changing the length and tension of vibrating coil

#### 18. A Duddell’s oscillograph can be used for frequencies

- Upto 50 Hz
- Upto 500 Hz.
- Above 500 Hz
- Upto 10KHz.

B. Upto 500 Hz.

#### 19. A Duddell’s oscillograph will give no amplitude distortion and phase displacement if its

- Moment of inertia and stiffness constant are zero
- Stiffness constant and damping factor are zero
- Moment of inertia and damping factor are zero
- All the above.

C. Moment of inertia and damping factor are zero

#### 20. In a Duddell’s oscilloscope the phase displacement of fundamental and 13^{th} harmonic are calculated to be 3° and 36° The oscillograph will show the 13^{th} harmonic to be

- 39° ahead of its true position
- 38° ahead of its true position
- 3° ahead of its true position
- 3° behind of its true position.

C. 3° ahead of its true position