Most of the previous year's questions from this chapter are from dimensional formulae and dimensional analysis. This questions can be solved easily if the physics course is completed. No need for memorizing all dimensional formula. Dimensional formulae can be derived from basic equations easily. For example
Question- Dimensions of, where symbols have their usual meaning, are (AIEEE 2003)
This can be solved using:
The relation speed of light Therefor dimension of a = dimension of =
For Example- calculation of absolute error for a set of readings of the period of a simple pendulum etc.
Let's see another example from Errors
Question- The percentage of errors in quantities P, Q, R, and S are 0.5%, 1%, 3%, and 1.5%
respectively in the measurement of a physical quantity
(JEE Main 2018)
The maximum percentage error in the value of A will be :
This can be solved using the concept :
Error in quantity raised to some power -- wherein
= absolute error in the measurement of a
= absolute error in the measurement of b
= absolute error in the measurement of x
Question- The respective number of significant figures for the numbers 23.023, 0.0003 and 2.1 x 10-3 are
4, 4, 2
5, 1, 2
5, 1, 5
5, 5, 2
1) 23.023 has 5 significant digits (Any zeros between two significant digits are significant)
2) 0.0003 has only 1 significant digit as zero to the left of first non zero digits are not significant.
3) 2.1 x 10-3 It has two significant digits (A final zero or trailing zeros in the decimal portion ONLY are significant).
Maximum Error in
1. Product x=a.b
2. Error in difference (x=a-b)
3. Error in division x = a/b
4. Error in quantity raised to some power
For the four sets of three measured physical quantities as given below. Which of the following options is correct ?
A quantity f is given by where c is speed on light, G is universal gravitational constant and h is the Plank's constant. Dimension of f is that of:
The dimension of stopping potential in photoelectric effect in units of Planck's constant 'h', speed of light 'c' and Gravitational constant 'G' and ampere A is :