VIVA QUESTION-MICROMETER SCREW GAUGE

MICROMETER SCREW GAUGE

Q.1: What is a screw?

Ans. Screw is a simple machine related to inclined plane.

Q.2: What is meant by “gauge”?

Ans. The gauge means device or instrument.

Q.3: Name two main parts of a screw-gauge?

Ans. (a) A nut (b) A bolt or screw

Q.4: What is meant by pitch of a screw?

Ans. Pitch is the distance between two nearest (consecutive or successive) threads along the axis of screw.

Q.5: How is the pitch found?

Ans. By dividing the distance covered by the screw in a known number of rotations by the total number of relations.

Q.6: What is the least count (L.C.) of the screw gauge?

Ans. L.C. of screw gauge = 0.001 cm.

Q.7: How the L.C. of a screw gauge is found?

Ans. By using the relation: L.C. = (Pitch of the screw / No. of circular scale divisions)

Q.8: What is meant by zero error of a screw-gauge?

Ans. The error which arises when the zero of circular scale does not coincide with the zero of the main scale upon joining the two studs.

Q.9: When the zero-error is positive?

Ans. If the zero of the circular scale lies above the reference line, provided that the fixed and movable studs are in contact.

Q.10: What is the degree of accuracy of the screw gauge?

Ans. Degree of accuracy = L.C. or Reading power = 0.001 cm

Q.11: What is mechanical advantage of a screw gauge?

Ans. Like a screw jack mechanical advantage of a screw gauge is 2π r/h; where ‘r’ is the radius of cylinder of the screw and ‘h’ is the pitch.

Q.12: What is meant by range of the screw gauge?

Ans. The maximum length of the main scale.

Q.13: What is formula for area of cross section of wire?

Ans. Area of circle = 2 π r

Q.14: What is back lash error?

Ans. Within a nut there is a little space for the play of screw. Due to continuous use this space increases. Thus when the screw is turned in one direction the stud moves as usual. However, when the screw is rotated in the opposite direction, the stud does not move for a while. This error is called Back lash error. In short “Back lash error is the error introduced on reversing the direction of rotation”.

Q.15: How back lash error is avoided?

Ans. By turning the screw in one direction only.

Q.16: What are “precision instrument”?

Ans. The instrument that can measure up to a fraction of a mm, e.g., vernier caliper, screw gauge and spherometer.

Q.17: What is Pi (π)?

Ans. Ratio between the circumference of a circle to its diameter. π = ( Length of Circumference / diameter )

Q.18: Does the diameter of the screw depend on temperature?

Ans. Yes it does. Diameter increases with the increase of temperature and decreases with the decrease of temperature.