# NAGALAND Class 11-science Physics Units and Measurement

#### Measurement and Error Analysis

Derived units are obtained from base units.

True value is the mean of all the observed readings.

Absolute error is the magnitude of the difference between the individual measured value and the true value.

The relative error is the ratio of mean absolute error to the mean true value.#### Significant Figures and Dimensions

Significant Figures in a measured value: Number of reliable digits plus the first uncertain digit.

Dimensional formula: Expression representing the physical quantity in terms of related base quantities.

Uses of Dimensional analysis to check the dimensional consistency of equations and to deduce relations among the physical quantities.