A wire 50 cm long and 1 mm² in cross-section carries a current of 4 A when connected to a 2 V battery. The resistivity of the wire is (a) 4 × 10⁻⁶ Ω m (b) 1 × 10⁻⁶ Ω m (c) 2 × 10⁻⁷ Ω m (d) 5 × 10⁻⁷ Ω m

Answer: (b). R = V/I = 2/4 = 0.5 Ω ρ = RA/l = 0.5 × 1 × 10⁻⁶0.5 ρ = 1 × 10⁻⁶ Ω m So the answer is (b) 1 × 10⁻⁶ Ω m.

A wire 50 cm long and 1 mm² in cross-section carries a current of 4 A… | NEET 1994 (AIPMT)

Q78NEET 1994 · AIPMTEasy

Ohm's Law, Resistivity & Temperature

A wire $50\text{ cm}$ long and $1\text{ mm}^{2}$ in cross-section carries a current of $4\text{ A}$ when connected to a $2\text{ V}$ battery. The resistivity of the wire is

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Answer: (b)

$R = \dfrac{V}{I} = \dfrac{2}{4} = 0.5\ \Omega$
$\rho = \dfrac{RA}{l} = \dfrac{0.5 \times 1 \times 10^{-6}}{0.5}$
$\rho = 1 \times 10^{-6}\ \Omega\text{ m}$
So the answer is (b) $1 \times 10^{-6}\ \Omega\text{ m}$ .

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