Least Count

Q. What is meant by least count? How can we calculate it?

Q.

A stop watch has 10 divisions graduated between the 0 and 5 s marks. What is its least count ?

Q.

Explain the meaning of the term 'least count of an instrument' by taking a suitable example.

Q.

How do you apply the correction due to zero error in the vernier caliper?

Q.

What is the normal weight of a human being?

Q.

A boy makes a ruler with graduations in cm on it (i.e., 100 divisions in 1 m). To what accuracy this ruler can measure ? How can this accuracy be increased ?

Q.

One cm on the main scale of the vernier caliper is divided into 20 equal parts and the number of vernier scale divisions is 10. The Z.E of the instrument is –0.45 mm. If an object is placed between the jaws of vernier calipers, the M.S.R and V.C.D are 12 M.S.D and 9, respectively. What is the length of the object?

1. 69 mm

2. 6.90 mm

3. 6.90 cm

4. 0.690 mm

Q.

Bigger the least count of an instrument, ___ the accuracy of the measurement made by the instrument.

Q.

The least count of an instrument is the ___ measurement that can be taken accurately with it.

Q.

Name the instrument which has the least count :

(a) 0.1 mm (b) 1mm (c) 0.01 mm.

Q.

The least count of a vernier caliper is 0.01 cm and if the length of the rod measured by it is 60.5 mm and observed vernier coincidence is 5, then the division of the main scale nearer to which zero division of vernier lies is _________.

1. $45$

2. $65$

3. $50$

4. $60$

Q. The given diagram represents a screw gauge. The circular scale is divided into $50$ divisions and the linear scale is divided into millimetres. If the screw advances by $1\text{mm}$ when the circular scale makes $2$ complete revolutions, find the least count of the instrument and the reading of the instrument in the figure.

Q.

What is the least count of a thermometer having 20 divisions between $0^{\circ }C$ and ${20}^{\circ }C$ mark?

1. 0

2. 15

3. 10

4. 20

Q.

Which of the following measures a small length to a high accuracy : metre rule, vernier callipers, screw gauge ?

Q.

Write the least count of the following measured value:

2.5 cm

Q. A student measured the length of a rod and wrote it as 3.50 cm . Which instrument did he used to measure it? (1) a meter scale with least count 0.1 cm (2) a vernier calliper where the 10 division in vernier scale matches with 9 division in main scale and main scale has 10 division in 1 cm (3) a screw gauge having 100 division in the circular scale and pitch as 1 mm (4) a screw gauge having 50 divisions in the circular scale and pitch as 1 mm Explain.

Q.

When an object is placed between the jaws of a vernier calliper, the M.S.R. is 3 mm and V.C.D. is 3 divisions. The maximum number of divisions on the vernier scale is 10 and the zero error of the instrument is +0.12 cm. What is the length of the object (in cm)?

1. 21

2. 0.021

3. 2.1

4. 0.21

Q.

If the Zero error of a Vernier Caliper is zero, then

1. measured length > actual length

2. measured length < actual length

3. measured length > = actual length

4. measured length = actual length

Q. 1. What is a micrometre screw gauge? $\left[1.5\text{marks}\right]$
2. State any one way to avoid backlash error in a screw gauge. $\left[0.5\text{mark}\right]$

Q.

Use the following information to answer the next question.

Akram has a piece of thread. He measures the length of a table using this thread. He has to place the thread eight times along the length of the table to measure its length. Then, he folds the thread twice at its mid point and again measures the length of the same table.

How many times does Akram have to place the folded thread along the length of the table?

1. 4

2. 8

3. 16

4. 32

Q. Which of the following measures a small length to a high accuracy,
a) Meter scale
b) Vernier callipers and
c) Screw gauge

1. Meter scale
   
2. Vernier callipers
   
3. Screw gauge
4. All of the above
   

Q.

While measuring the length of a copper rod using Vernier calipers, the zero of the Vernier scale was found to be between 4.6 cm and 4.7cm on the main scale. The 6th division of the Vernier scale is found to coincide with a division on the main scale. Find the length of the rod if the least count is 0.01 cm.

Q. A stop watch has 10 divisions graduated between the 0 and 5 s marks. Its least count is $\frac{x}{2}sec,$ find the value of x.

Q.

Write the least count of the following measured value.

0.007cm

Q.

A vernier calliper was used to measure the diameter of a ball and the measurement was reported as 2.35 cm. What could be the least count of the instrument?

1. 1039

2. 1039.784

3. 1040

4. 104

Q. 7.0 is more precise than 7.00.

1. False
2. True

Q.

The scales - vernier callipers, metre scale and screw gauge has the least counts:

1. 0.1 mm, 1 mm, 0.01 mm respectively

2. 0.001 mm, 1 mm, 0.01 mm respectively

3. 0.1 mm, 0.1 mm, 0.01 mm respectively

4. 0.01 mm, 1 mm, 0.001 mm respectively

Q. The least count of a vernier callipers is 0.1 mm.

1. True
2. False

Q.

Find the least count of a screw gauge whose least count of linear scale is 1 mm and the circular scale is divided in 50 divisions and 2 entire rotations makes to 1 division on linear scale.

1. 0.01 mm

2. 0.02 mm

3. 0.2 mm

4. 0.1mm

Q. Smaller the least count of an instrument, more precise is the measurement made by using it.

1. True
2. False