Page 25 - Physics - XI

Q9. Why is a screw gauge so named?
Ans. The diameters of wires are governed by some standard number called standard wire gauge (S.W.G.).
As the instrument measures these diameters, it is called a screw gauge.

Q10. What is the main characteristic of the screw?
Ans. The linear distance travelled by the screw is directly proportional to the number of rotations given
to it.

Q11. What is backlash error? Why is it caused?
Ans. Due to wear and tear, the screw becomes loose in the nut and may not move forward when turned
in the nut. Error due to this is called backlash error.

Q12. How can you minimise backlash error?
Ans. It can be minimised by turning the screw always in one direction while taking observations.

Q13. Give the least count of the screw gauge that you used in the experiment.
Ans. The least count of commonly used screw gauge is 0.001 cm.

Q14. What is the zero error of the screw gauge?
Ans. When movable screw tip B comes in contact with stud A and zero mark of the circular scale does not
coincide with the reference line of the main scale, the screw gauge has an error called zero error.

Q15. What is the positive zero error of the screw gauge?
Ans. If the zero of the circular scale is below the reference line when stud A and B just touch each other,
the zero error is positive.

Q16. What is the negative zero error of the screw gauge?
Ans. If the zero of the circular scale is above the reference line when stud A and B just touch each other,
the zero error is negative.

Q17. How is zero correction related to zero error?
Ans. The zero correction is the negative of the zero error.

Q18. What are the reasons for zero error in a screw gauge?
Ans. The zero error arises due to the wear and tear of a screw and manufacturing defect.

Q19. Can zero error be minimised in a screw gauge?
Ans. No

Q20. We have two screw gauge having same number of divisions on circular scale, but their pitches
are 0.5 mm and 1.0 mm. Which screw gauge is more accurate?
Ans. The screw gauge whose pitch is 0.5 mm is more accurate.

Q21. What is the micrometer?
Ans. It is the other name for screw gauge.

Q22. How can you fi nd the thickness of a paper by a screw gauge?
Ans. We fi nd the thickness of 50 sheets of paper and then divide this value by 50 to get the thickness of
paper.

Q23. Can backlash error be avoided completely?
Ans. No

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