Vernier callipers and screw gauge — practice questions

Question 1 · difficulty L1 · recall

The least count of a Vernier calliper is the smallest length it can reliably resolve, commonly found from

• A. one main-scale division minus one Vernier-scale division for a direct Vernier
• B. main-scale length multiplied by object mass
• C. pitch divided by wire radius
• D. zero error only

Question 2 · difficulty L1 · understanding

For a screw gauge, least count equals

• A. pitch multiplied by circular divisions
• B. pitch divided by number of circular-scale divisions
• C. diameter divided by pitch
• D. main-scale reading plus zero error

Question 3 · difficulty L2 · understanding

A screw gauge has pitch 0.5 mm and 50 circular divisions. Its least count is

• A. 0.1 mm
• B. 0.025 mm
• C. 0.01 mm
• D. 25 mm

Question 4 · difficulty L2 · application

A Vernier reading is obtained by adding main-scale reading to

• A. zero error regardless of sign
• B. object radius squared
• C. pitch × main-scale divisions
• D. coinciding Vernier division × least count

Question 5 · difficulty L3 · application

If an instrument has a positive zero error, the zero correction is

• A. negative
• B. positive
• C. zero
• D. equal to the measured value

Question 6 · difficulty L3 · application

A screw gauge shows main-scale reading 5.5 mm and circular division 23 with least count 0.01 mm, with no zero error. The reading is

• A. 5.23 mm
• B. 5.73 mm
• C. 5.50 mm
• D. 7.80 mm

Question 7 · difficulty L4 · analysis

Why should a screw gauge ratchet be used gently?

• A. To change the least count during measurement
• B. To eliminate pitch permanently
• C. To apply nearly consistent small contact force and avoid deforming the object
• D. To reverse the screw thread

Question 8 · difficulty L4 · analysis

Several diameter readings of a wire are taken at different orientations with a screw gauge. The main purpose is to

• A. increase zero error deliberately
• B. change the pitch
• C. avoid applying zero correction
• D. reduce random error and detect nonuniformity

Question 9 · difficulty L5 · analysis

A calliper has least count 0.01 cm and positive zero error +0.03 cm. If observed reading is 2.46 cm, corrected reading is

• A. 2.43 cm
• B. 2.49 cm
• C. 2.46 cm
• D. 2.40 cm

Question 10 · difficulty L5 · analysis

Which practice best reduces parallax while reading a linear scale?

• A. View from a strongly oblique angle
• B. View the mark with the eye approximately normal to the scale at the index
• C. Move the object during reading
• D. Ignore the reference line