Question

A screw gauge has 50 divisions on its circular scale. The circular scale is 4 units ahead of the pitch scale marking, prior to use. Upon one complete rotation of the circular scale, a displacement of 0.5 mm is noticed on the pitch scale. The nature of zero error involved, and the least count of the screw gauge, are respectively.

(1) Positive, 0.1 mm 

(2) Positive, 10 μm 

(3) Negative, 2 μ m 

(4) Positive, 0.1 μ m

Answer 1

Correct answer is (2) Positive, 10 μm 

Answer 2

Correct Answer : Option B

Solution

Since the screw gauge is ahead by 4 units that means for an actual length of zero the instrument read 4(LC) which is more .

error= Length measure by faulty instrument- actual length

error here is positive

LC= Pitch/CSD ( CSD stands for no. of circular scale divisions)

=0.5/50 mm = 0.01 mm = 10 micrometer