Civil Engineering - UPSC Civil Service Exam Questions - Discussion

@All.

Here, There are two cases possibilities;

1. The temperature of the field is greater than the temperature at which the tape is standardized; Tm > To. This results in an increase in the tape length, making the measured length shorter. Hence the correction is additive.

2. The temperature of the field is lesser than the standardized temperature, i.e. Tm<To, then the tape length decreases. This results in an increase in the measured length than the original. Hence the correction is subtractive.

So, options c is the correct answer

Let me explain>

The formula for correction C=α(tm -t)L.

So,α= 0.0000112.

Also l= 30m.

Also, temp measured = 15 degrees.
And temp star = 20 degree.

Solving we get -0.001680 but in the question it
Is for per metre tape length so divide by 30.

We get a correction - 0.0000560 but he has asked for error so + 0.0000560 is the correct answer.

Here it is behaviour as a short chain because temperature decrease than standard temp. In short chain error will be positive and correction will be negative so option A and D is wrong.

Because the questions asks Error due to temperature not correction. Per tape length not per 1m tape length. So C is correct.

C is correct.
m = 15'
To = 20'.

The temperature at the time of measurement is less than standard temperature so tape length will decrease and the error will be positive.

Correction is negative and error is possitive.
Per tape, length means per 30 m not per 1 meter what will be the error.
So it is 0.00168m.

In question asked per tap length so;
C/L = 00112*(15-20).
So. = -00560 will be answer.
So option A is correct.

Use formula, temp correction = L α t = 90x0.0000112x(15-20) = -0.00168 m.

Correction is negative than error is positive so I think C is correct option.

No @Aman.

Here, Tm>To so error will be -ve and correction will be +ve.

@Rahulkhan:

Why L is taken as 90 when It's given as 30 in the question?

It's not per meter tape length, it's per tape length So D is correct.