Question

Possible errors with a screw gauge are:
A.) Systematic error
B.) Backlash error
C.) Personal error
D.) All of these

Answer 1

Hint: Systematic errors occur due to slight imperfection in the measurement technique of an individual (personal error) or due to defects in the apparatus (such as zero error). This error is highly possible while measuring with a micrometer screw instrument such as the screw gauge.

Complete step by step answer:
Systematic error is the name given to the class of errors that occur due to imperfect or wrong technique of measurement of the user or an inherent defect in the device.

1.) The imperfections in the measuring technique of a user are termed as personal errors. These vary from person to person and depend upon the ability level and experience of the user.

2.) Some errors arise due to the defect in the measuring instrument. These are very common in micrometer screw type measuring devices such as the screw gauge. One such error is the zero error which happens when the zero of the main scale and the circular scale do not match when the jaws are closed.

3.) Another common error due to a defect in the apparatus is the backlash error. This is also very common in micrometer screw type measuring instruments. In this, the backward rotation of the screw does not bring about a simultaneous backward movement in the scale. The scale remains stuck for a small part of the initial rotation. This causes an error in the measurement.

These two instrument defects come along with personal errors already come under systematic errors.

Hence, the correct option is A) systematic error.

Note: Students not knowing the definitions of errors properly will get confused in this question. They may be tempted to mark backlash error as the correct option since it is one of the most common errors in a screw gauge. However backlash errors and personal errors already come under the definition of systematic errors. Hence, the most appropriate answer for this question is systematic error.
Students should not ignore this topic since these instruments form the basis of performing practical experiments in the laboratory which is essential for learning physics. Even from an examination point of view, these questions are very scoring and take very less time. A student who can answer these questions, especially in competitive exams, will definitely have an edge over others.