Question

A boy uses a vernier callipers to measure the thickness of his pencil. He measures it to be $1.40\text{mm}$. If the zero error of vernier callipers is $+0.02\text{cm}$, what is the correct thickness of the pencil?

• A. $1.38\text{mm}$
• B. $1.20\text{mm}$
• C. $1.60\text{mm}$
• D. $1.42\text{mm}$

Answer 1

The correct option is B $1.20\text{mm}$

Measured thickness of the pencil (observed reading) $=1.40\text{mm}$

Zero error $=+0.02\text{cm}=+0.20\text{mm}$
[Since $1\text{cm}=10\text{mm}$]

Correct reading = Measured reading $-$ zero error
Hence, Correct reading$=1.40\text{mm}-0.20\text{mm}=1.20\text{mm}$