JEE Advanced 2020 Concept Recapitulation Test 1 Paper 1

Given, voltage V=(100±5)V
Current I=(10±0.2)A
According to Ohm's law, V=IR or R=V∕I
Taking log of both sides,
log‌R=log‌V−log‌I
Differentiating, we get
‌

∆R

R

=‌

∆V

V

−‌

∆I

I

For maximum error,‌

∆R

R

=‌

∆V

V

+‌

∆I

I

Multiplying both sides by 100 for taking percentage, we get
‌

∆R

R

×100=‌

∆V

V

×100+‌

∆l

I

×100
Percentage error in resistance R
=‌

∆V

V

×100+‌

∆l

I

×100
=‌

5

100

×100+‌

0.2

10

×100=7%.