Showing posts with label important bits. Show all posts
Showing posts with label important bits. Show all posts

Sunday, December 24, 2023

MCQ'S ON ELETRICAL MEASURMENTS

 1.Deflection methods of direct  measurements are most widely used as these are 

a) mostly simple

b)most accurate 

c)least time consuming

d) most simple and least time consuming 

ans : d

2 Comparison methods are used

a)because these are most simple

b)because these are inexpensive

c)because these take least time in measurement

ans: d

3 The main advantage of the null balance technique of measurement is that  

a)it does not load the medim

b)it gives a centre zero value as its input 

c)it gives a quick measurement

d)it is not affected by temperature variation 

ans:a

4 The region between the limits within which a quantity is measured received or transmitted ,expressed by stating the lower and upper limits is called the

a) range

b) span

c)range limit

d)none of these 

ans : a 

5 The span of a zero-centers voltmeter having a scale from -10v to10v is

a) 0V

b) -10v

c)10v

d)20v

ans :d

6 if two meters X & Y require 40mA &50mA respectively,to give full deflection,then

a)X is more sensitive 

b) Y is more sensitive 

c)both  are sensitive

d)it is not possible to asses with the data given

ans :a

7 A meter having a sensitivity of 2kOhm/V is used for the measurement of voltage across a circuit having an output resistance of 1kohm and open circuit voltage of 8V.What is the meter at its 10V scale

a)57.2V

B)6.51V

c)7.62V 

d)7.91V

ans c

8 The smallest change in a measured variable to which an instrument will respond is 

a)accuracy

b)resolution

c)precision

d)sensitivity 

ans b

9 Resolution of an instrument of an instrument is 

a) the minimum quantity it can measure 

b) the maximum quantity it can measure

c)the maxiumum nonlinearity 

d)ablility to distinguish polarity 

ans: a 

10 Hysteresis in an instrument means

a) the change in same reading when the input is first increased and then reduced 

b)the reliablity if the instrument 

c)the repeatability of the instrument 

d)the inaccuracy due to change in temperature

ans :a

11 The static error band of an instrument implies the

a) accuracy of the instrument

b) the irrepeatability of the instrument 

c)error caused when the pen stopped at some deflection

d) error introduced in low varying inputs

ans: c 

12 the static error band of an instrument does not include 

a)non linearity

b)electric drift

c)hysteresis in the instrument

d)non of these 

ans :b

13 the fact as to how closely the instrument reading follows is measured variables is called the

a)accuracy

b)precision

c)fidelity

d)sensitivity

ans :c

14 An higher scale ammeter is used to measure too low current The measurement would have low

a) precision

b)accuracy

c)resolution

d)all of the above

ans:d

15 Thermal zero-shift in an instrument refers to

a)maximum variation in pen zero due to temperature variation

b)inaccuracy in measurement due to temperature variation

c)shift in zero adjustment due to expansion of springs due ti temperature variation 

d)non of the above

ans a

 

 


 



 



 

 


Monday, December 24, 2018

MCQ'S ELECTRICAL ENGINEERING MATERIALS





01․ ________ is the most detrimental impurity in the magnetic materials
 Carbon.
 Sulphur.
 Oxygen.
 Nitrogen.

02․ How many classes of insulating materials are there?
 6.
 7.
 5.
 8.

03․ What are insulating materials that can tolerate maximum temperature?
 Mica.
 Porcelain.
 Glass.
 All of these.

04․ What is the value of dielectric constant of air?
 Less than 1
 0.
 1.
 none of these.


05․ Which of the following is the example for piezo-electric material ?
 Lead zirconate titanate
 Copper
 Potassium niobate
 None of the above


 Zinc silicate.
 Calcium silicate.
 Zinc sulphide.
  Magnesium silicate.

07․ Which of the following is the least desired property in magnetic materials for electrical engineering applications ?
 High magnetic permeability.
 High electrical resistivity.
 Large hysteresis loop.
 All of the above.


08․ The magnetisation and applied field in ferromagnetic materials are related
 sinusoidally.
 non linearly.
 linearly.
 parabolically.

09․ The materials which exhibit the same elastic properties in all directions are called
 isotropic.
 isentropic.
 inelastic.
 visco elastic.

10․ The dielectric strength of ferroelectric materials depends to a large extent on
 area of hysteresis loop for the material.
 presence of magnetic materials in the vicinity.
 intensity of electric field.
 frequency of applied voltage.

FOR ANSWERS CLICK HERE HERE

11․ The potential gradient across the material of low permittivity is ______________ than across the material of high permittivity.
 greater.
 smaller.
 both (A) and (B).
 none of above.

12․ Materials which lack permanent magnetic dipoles are called
 dia-magnetic.
 ferro-magnectic.
 semi-magnetic.
 none of the above.

13․ Which of the following is the ferroelectric material ?
 Rochelle salt.
 Potassium dihydrogen phosphate.
 Barium titanate.
 All of the above.


14․ Materials having a high dielectric constant, which is non-linear, are known as
 elastomers.
 ferroelectric materials.
 super die-electrics.
 hard die-electrics.

15․ In ferromagnetic materials
 the atomic magnetic moments are antiparallel and unequal.
 the atomic magnetic moments are parallel.
 the constituent is only iron.
 one of the constituent is iron.


16․ A material with unequal anti-parallel atomic magnetic moments is
 ferrimagnet.
 an anti-ferromagnet.
 a ferrite.
 non-magnetic.


17․ The permanent magnets are made from which of following materials ?
 Soft iron.
 Ferromagnetic.
 Paramagnetic.
 Diamagnetic.

18․ Indicate which of following material does not retain magnetism permanently
 soft iron.
 stainless steel.
 hardness steel.
 none of above.

19․ Which statement is not true of ferromagnetic materials.
 Energy loss is proportional to the area of hysteresis loop.
  They have fixed value of μr.
 They have large magnetic susceptibility.
 They lose their nonlinearly property above the Curie temperature.

20․ Which of following material has least value of dielectric constant?
  Paper.
  Oil.
  Ceramics.
  Glass.
21․ In order to minimise loss due to hysteresis, the magnetic material should have
  high resistivity.
  low hysteresis coefficient.
  large B-H loop area.
  high retentivity.

22․ In electrical machines the material preferred for pole shoes of electromagnets is
 copper.
 aluminium.
 pure iron.
 lead.

23․ Which of the following gives materials in order of decreasing values of permeability?
  Permalloy, nickel, air, water.
 Cobalt, nickel, aluminium, iron.
 Pure iron, silicon iron, aluminium, bismuth.
 Silver, copper, aluminium, iron.