Question

Screw gauge is said to have a negative error

• A. when head scale zeroth division coincides with base line of main scale
• B. when head scale zeroth division is above with base line of main scale
• C. when head scale zeroth division is below with base line of main scale
• D. None of the above

Answer 1

The correct option is B when head scale zeroth division is above with base line of main scale

When head scale zeroth division is above base line of main scale, it means that at zero reading, it is showing a positive value and hence this needs to be subtracted from the measured value. Hence the error is a negative error.