This Portion of Electrical andElectronic Measurements and Measuring instruments contains Units, Systems, Dimensions and Standards MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.

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

- Units, Absolute Units, Fundamental and Derived Units
- Dimension, Dimension of Mechanical Quantities
- CGS System of Units
- Relationship between Electrostatic and Electromagnetic System of units
- MKS System
- SI Units
- Supplementary Units
- Absolute measurement of Currents and Resistance
- Standards and their Classification, Standards for mass and length
- Atomic Frequency and Time Standards
- Temperature Standards
- Luminous intensity standards
- Electrical Standards
- Emf Standards
- Resistance, Current, Inductance , Capacitance Standards

#### 1. A coherent system of units is to be evolved which has N kinds of quantities to evaluate and M independent physical quantities expressing relationship between them, we can independently choose the sizes of units of :

- N+M quantities
- N-M quantities
- N quantities
- M quantities

B. N-M quantities

#### 2. The units whose sizes cannot be chosen independently are called :

- Derived units
- Fundamental units
- Absolute units
- Auxiliary fundamental units.

A. Derived units

#### 3. The dimension of inductance in CGS s system are :

- [
*ԑL*^{-1}*T*^{2}] - [
*ԑ*^{-1 }ML^{-1 }*T*^{2}] - [
*ԑ*^{-1}LT^{-2}] - [
*ԑ*^{-1 }L^{-1 }*T*^{2}]

D. [

*ԑ*^{-1 }L^{-1 }*T*^{2}]#### 4. The dimension of resistance CGS e.m. System are :

- [µ
^{-1}*LT*^{-1}] - [µ
^{-1 }*MLT*^{-1}] - [µ
*LT*^{-1}] - [µ
*LT*^{-2}]

C. [µ

*LT*^{-1}]#### 5. The base units in SI system are

- Metre, kilogramme, second
- Metre, kilogramme, second, ampere
- Metre, kilogramme,second, ampere, Kelvin, candela, mole
- Metre, kilogramme, second, ampere, Kelvin, candela

C. Metre, kilogramme,second, ampere, Kelvin, candela, mole

#### 6. The symbole nm stands for :

- newton metre
- nano metre
- nano milli
- number of moles.

B. nano metre

#### 7. In measuring the absolute value of ampere using Rayleigh’s balance, the value of gravitational constant g must be accurately known because :

- The expression for the force is in Newton and weights used in counterbalancing the force are in kg
- Value of g is different at different places
- Corrections have to be made for the weight of moving coil
- None of the above.

A. The expression for the force is in Newton and weights used in counterbalancing the force are in kg

#### 8. In Lorenz method for absolute measurements of ohm, two measurements are made one with current in one direction and the other with current in the opposite direction. This is done to :

- eliminate the effect of thermal emfs
- eliminate the effect of earth’s magnetic field
- eliminate the effect of both thermal emfs and earth’s magnetic field
- eliminate the effect of both temperature on coil and disc.

C. eliminate the effect of both thermal emfs and earth’s magnetic field

#### 9. The international standard of length is defined in terms of :

- Length of earth’s meridian passing through paris
- Distance between two lines engraved on a platinum-iridium bar
- Wavelength in vaccume, of radiation of krypton -86 atom in its two specified transitions
- None of the above.

C. Wavelength in vaccume, of radiation of krypton -86 atom in its two specified transitions

#### 10. The most stable primary atomic standard for frequency is :

- Caesium beam standard
- Hydrogen maser standard
- Quartz standard
- Rubidium vapour standard.

B. Hydrogen maser standard

#### 11. Caseium beam standard is normally used primary atomic standard for frequency because :

- Caesium beam standard has an accuracy 3 parts in 10
^{12 }, has short term stability , low drift and small size. - Hydrogen master standard, though it the most stable frequency source but has a large size.
- Quartz crystal’s operating frequency changes with change in load capacitance and also the drift in frequency is asymptotic with time
- All the above.

D. All the above.

#### 12. The disadvantage of atomic standards are :

- Their accuracy is lower than that of standards based upon astronomical measurements
- The time taken for measurements is long
- The results obtained with atomic standards are not uniform
- None of the above.

D. None of the above.

#### 13. The maximum current that can be drawn from a saturated Weston Cell without damaging it,is

- 100MA momentarily
- 100µA continuously
- 100 µA momentarily
- 1 mA momentarily

C. 100 µA momentarily

#### 14. The internal resistance of a saturated Weston Cell is of the order of :

- A few ohm
- A few kilo ohm
- A few hundreds of ohm
- A fraction of ohm

C. A few hundreds of ohm

#### 15. The decrease in the value of emf of an unsaturated Weston Cell is :

- About 1 µ V per year
- About 1 mV per year
- About 5 – 10 µ V per year
- About 30 – 50 µ V per year

D. About 30 – 50 µ V per year

#### 16. Zener sources when used as voltage standards :

- Are reversed biased
- Can be designed to cover a wide range of voltages
- Are immune to the effect of short circuits
- All of the above.

D. All of the above.

#### 17. The output voltage Josephon effect standard :

- Can be changed in a continuous manner
- Can be changed only in a discrete steps
- Can be changed continuously as well as in discrete steps
- Can not be changed

B. Can be changed only in a discrete steps

#### 18. Candela can be defined as the luminous intensity in the perpendicular, of a surface of :

- 1/2 59000 square metre of a full radiator
- 1/600 square centimeter of a full radiator
- 1/5,89,000 square metre of a full radiator
- 1/600, 000 square metre of a full radiator

D. 1/600, 000 square metre of a full radiator

#### 19. The material of wires used for making resistance standard is usually :

- Manganin
- Nichrome
- Copper
- Phosphor Bronze.

A. Manganin

#### 20. In order to reduce skin effect in resistance standards when they are used on high frequency a.c :

- The diameter of the resistance wire should be small
- Adjacent turns of the resistance coil should carry currents in the opposite direction
- They should be provided with four terminals
- All of the above

A. The diameter of the resistance wire should be small