Question

The specific resistance `rho` of a circular wire of radius `r`, resistance `R`, and length `l` is given by `rho = pi r^(2) R//l`. Given : ` r = 0.24 +- 0.02 cm , R = 30 +- 1 Omega` , and `l = 4.80 +- 0.01 cm`. The percentage error in `rho` is nearly
A. `7 %`
B. `9%`
C. `13 %`
D. `20%`

Answer 1

Correct Answer - D
Required percentage
`= 2 xx ( 0.02)/( 0.24) xx 100 + (1)/( 30) xx 100 + ( 0.01)/( 4.80) xx 100`
` = 16.7 + 3.3 + 0.2 = 20%`