Class 11th | physics Viva-Voce Question Answers

Q.1 What is vernier constant?

Ans. The difference between the values of one main scale division and one vernier scale division is

called vernier constant

Q.2 What is zero error ?

Ans. lf zero of main scale does not coincide with zero of vernier scale when the two jaws of the

vemier calliper touch each other, the instrument is said to have zero errors.

Q.3. What is vernier callipers? Why is it so called ?

Ans. Itis an instrument used to measure small length, i.e., fractions of a millimeter accurately. It was

invented by French Mathematician Pierre Vernier. Thus this instrument is called Vernier Calli-

pers.

Q.4. What is meant by least count (LC) of a measuring instrument ?

Ans. The least count of a measuring instrument is smallest value of physical quantity which can be

measured by the instrument.

Q.5. What is meant by zero error of vernier callipers ?

Ans. On bringing the of jaws  Vernier callipers in contact with each other, the zero of the vernier scae

in some instruments does not coincide with the zero of the main scale. Such instruments are

said to possess a zero error.

Q.6. Why is vernier scale used ?

Ans. To increase the accuracy of measurement.

Q.7. When is zero error positive and when is it negative ?

Ans. When vernier scale zero is right to the zero of main scale, it is positive, and when vernier scale

zero is left to the zero of main scale zero, zero error is negative.

o.8. What is principle of vernier scale ?

Ans. The number of vernier divisions, i.e., 10 divisions are exactly equal to 9 main scale divisions.

 i.e., 10 VSD =9 MSD.

Q.9. How does zero error arise in a vernier callipers?

Ans. It arises because of the wear and tear due to long use or due to some manufacturing defect.

O.10. How do you determine the sign of zero error?

Ans. If the zero of the vernier scale lies to the right of the zero of main scale, when the two jaws of the

vernier callipers are brought in contact with each other, the vernier callipers is said to possess

positive zero error. On the other, hand, if the zero of the vernier scale lies to the left of the zero

of main scale, it is said to possess negative zero error.

Q.11. What is the difference between least count and vernier constant ?

Ans. Least count is the smallest quantity that can be measured by an instrument.

Vernier constant is the special name given to the least count of the vernier callipers.

Q.12. What is the function of the jaws projecting on the other side in a vernier callipers ?

Ans. These are provided to measure the internal diameter of a calorimeter, a glass tube, etc.

Q.13. Is there any other type of vernier ?

Ans. Yes. In a sextant or a spectrometer, angular (or circular) vernier is used to measure the angle

accurately.

Q.14. Give the density of water, ice and mercury in S.I.

Ans. In S.I , the density of water, ice, and mercury are 1,000 kg m‐³, 930 kg m‐³and 13,600 kg m‐³

respectively.

Q.15. Define density. Give its S.I. unit.

Ans. It is defined as mass per unit volume of a substance. In S.I., the unit of density is kg m‐³

Q.16. Why do we measure the diameter of a spherical /cylindrical body in two mutually perpen-

dicular directions?

Ans. If the diameter of a spherical/cylindrical body decreases in one direction on being subjected to

a strain, then it will increase in a direction perpendicular to it. The mean of the diameters mea-

sured in two mutually perpendicular directions gives the correct value of the diameter of the

body.

Q.17. Is the value of density of a substance same in all the systems of units?

Ans. No, it is different in different systems of units. For example, density of water is 1g cm‐³in c.g.s

system and 1,000 kg m‐³ in S.I

Q.18. How does density vary with temperature ?

Ans. Normally, it decreases with the increase of temperature of a substance. However, in case of

water, it increases from 0°C to 4"C and above 4°C, it decreases with increase of temperature. In

other words, the density of water is maximum at 4°C.

Q.19. Are the two terms-density and relative density of a substance have the same meanings ?

Ans. No, the two terms are quite different in their meanings. The density of a substance is the mass of

a substance per unit volume. It is a dimensional quantity and has units. On the other hand, the relative density of a substance gives the quantitative of how many times it is heavier than another given substance (usually water at 4°C ).It is a dimensionless quantity and has no units .

Q 20. What do you mean by least count of measuring instrument ?

Ans. The least count ofa measuring instru-ment is the least quantity which can be mea

-easured precisely with the help of that instrument.

Q 21. What is the least length that can be measured with a given vernier.

Ans. Equal to its least count (i.e., vernier constant).

Q22.What is the value of vernier constant of a common vernier callipers .

Ans. 0.1 mm or 0.01 cm.

Q. 23. Mention some common uses of vernier callipers.

Ans. To measure the length, breadth, external and internal diameters and depths of the hollow vessels.

Q. 24. Where is a body kept, whose length is to be measured ?

Ans. Between the jaws of a vernier callipers.

Q.25. What is the function of smaller pair of jaws?

Ans. To measure the internal diameter of hollow bodies.

Q.26. Doyou know any other instrument where the principle of vernier is used ?

Ans. Yes, Fortin's barometer, travelling micro-scope, sextant spectrometer, polarimeter etc.

Q.27. Can we measure the thickness of a piece of a paper by vernier callipers ?

Ans. No, because its thickness is less than the least count of a vernier callipers.

Q.28. When the zero error is positive and when negative?

Ans. Zero error is positive when vernier zero is to the right of main scale zero and negative if it is to

the left.

Q.29. How can the accuracy of the spherometer be increased?

Ans. The accuracy can be increased by making the least count smaller either by decreasing pitch or by

taking a large disc with greater number of divisions on it.

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