JEE Main · 2026 · 05 Apr 2026 · Shift 2 · Units & Measurement

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In an experiment to determine the resistance of a given wire using Ohm's law, the voltmeter and ammeter readings are noted as 10 V and 5 A, respectively. The least counts of voltmeter and ammeter are 500 mV and 200 mA, respectively. The estimated error in the resistance measurement is ______

Ω

(A)0.25
(B)2
(C)2.5
(D)0.18✓ Correct

Answer: (D)

Solution

By Ohm's law the resistance is

R = \frac{V}{I} = \frac{10}{5} = 2 Ω

. For a quotient the fractional errors add,

\frac{Δ R}{R} = \frac{Δ V}{V} + \frac{Δ I}{I}

, where the least counts give the absolute errors

Δ V = 0.5 V

and

Δ I = 0.2 A

. Thus

\frac{Δ R}{R} = \frac{0.5}{10} + \frac{0.2}{5} = 0.05 + 0.04 = 0.09

, and

Δ R = 0.09 \times 2 = 0.18 Ω

. The estimated error in the resistance is

0.18 Ω

JEE Main · 2026 · 05 Apr 2026 · Shift 2 · Single correct option

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