Page 29 - Electrostatics-11

© GC Shiba

Error: Scattering of observed data from standard value is called error. Physically

it is not the mistake. In physics, we can minimize the error but can’t get the physics
error free.
Relative error: The error which is expressed in terms of percentage is called
relative error or percentage relative error.

= × %

Least count: An instrument that can defined the smallest unit of measurement
called least count. For e.g., least count for cm scale is 1 mm.

Accuracy and Precision

Accuracy Precision

Accuracy is the degree of closeness of Precision is the degree of closeness
measured value to the true value. reading to the mean value.
The measurements are more accurate if The measurements are more precise if

the measuring instrument is proper and the instrument has smaller least count.
the readings are taking skillfully.
E.g., If a digital clock shows 5:15:25 E.g., If a digital clock shows 5:15:25

AM, the timing may or may not have AM, the timing is said have a good
good accuracy. precision.

Significant figure: The meaningful digits in a number are called significant
figure. The number of digits in a measurement about which we are certain plus one

additional digit which is uncertain are known as significant figures.
For e.g., suppose the length of scale is exactly 5 cm. Three different persons
measures the length of scale and record the observation as 5.0 cm, 5.00 cm and
5.000 cm respectively. Although these observations are identical from the

mathematical point of view but they are different from scientific point of view.
nd
The first measurement has 2 significant figures, 2 has 3 significant figures and
rd
3 has 4 significant figures. Obviously, the measurement has been made with
devices of different least count. Hence, the last measurement is most accurate from
scientific point of view.
1234 has 4 significant figures, 1001 has 4 significant figures, 0.001 has 1

significant figure, 864000 has 3 significant figures.

Order of magnitude: The number which is expressed in the base power of 10

is called order of magnitude.

6 Mechanics