Question

in a simple electric circuit, the current in resistor is measured as (2.50+_0.05)mA. the resistor is marked as having a value of 4.7ohm+_2 %
if these values were used to calculate the power dissipated in the in the resistor . what would be the percentage uncertainty in the value.
a)2%
b)4%
c)6%
d)8%

Answer 1

answer : option (C) 6%

explanation : first find percentage uncertainty in the current.

so, percentage uncertainty in current = ∆i/i × 100

here, ∆i = 0.05 and i = 2.5

so, % uncertainty in current = (0.05)/2.5 × 100 = 2%

we know, power dissipated is given by P = i²R

so, percentage uncertainty in power = 2 × % uncertainty in i + % uncertainty in R

= 2 × 2% + 2%

= 4 % + 2% = 6 %

hence, option (C) is correct choice.

Answer 2

Explanation:

option c is the correct answer