Question

The zero error of a Vernier is +2. Its zero correction is (take L.C = 0.01cm)
(A) 0.2 cm
(B) -0.2 cm
(C) -0.02 cm
(D) +0.02 cm

Answer 1

Hint: In order to solve this question first we will define the term zero error according to the property of vernier scale and the process of assigning zero error of any instrument, we will try to find out the zero correction on the basis of scale of Vernier and its least count.

Complete step-by-step solution -

Zero error is defined as the condition where a measuring instrument records a reading when no reading is required.
In case of Vernier calipers it occurs when a zero on the main scale does not coincide with a zero on Vernier scale it is called zero error for Vernier.
The zero error can be of two types: it is positive when the scale is higher than zero; otherwise it is negative. The process for using a Vernier scale or zero-error caliper is using the formula:
Actual scale reading = main scale reading + Vernier scale reading − (zero error found).
Positive zero error refers to the case when the reading of the scale is a positive reading away from the actual reading of 0.00 mm. If the reading is 0.20 mm, the zero error is referred to as +0.20 mm.
So, when the zero error is positive, it will be subtracted from the total reading.
Thus, zero correction for the Vernier scale is:
$
   = - \left( {2 \times L.C.} \right) \\
   = - \left( {2 \times 0.01} \right){\text{ }}\left[ {\because L.C. = 0.01\left( {{\text{given}}} \right)} \right] \\
   = - 0.02cm \\
 $
Hence, if the zero error of a Vernier is +2. Then its zero correction is -0.02cm.

So, the correct answer is option C.

Note- A Vernier scale is a visual aid for accurate measurement reading using mechanical interpolation between two linear graduation marks; thus increasing precision and reducing measurement uncertainty by using Vernier acuity to minimize human calculation error. The smallest value which the measuring instrument can measure is called its lowest count. Measured values are only fine up to this stage.