Question

The main scale reading of a vernier calliper is obtained as 3.2 cm for an object placed in it. If the 4th division of the vernier scale coincides with a division on the main scale, and the magnitude of the positive zero error is 0.03 cm, what is the true length of the object in cm? Take L.C. = 0.01 cm.

• A. $3.210\text{mm}$
• B. $3.210\text{cm}$
• C. $0.321\text{m}$
• D. $0.321\text{cm}$

Answer 1

The correct option is B $3.210\text{cm}$

Given:
Main scale reading (MSR) = $3.2cm$
Vernier scale reading that coincides with a division on the main scale, $p=4$
VSR = $p\times \text{L.C.}$
$=4\times 0.01=0.04cm$
Observed length of the object, $X$ = MSR + VSR $=3.2+0.04=3.24cm$
Magnitude of positive zero error, PZE = $0.03cm$
Positive zero error is subtracted from the observed length to get the true length.
$⟹$ True length = X - PZE = $3.24-0.03=3.21cm$