Question

The resistance of a wire of length 300 m and cross-section area 1.0 mm2 made of material of resistivity 1.0 x 10-7 Ω m is :; A. 2 Ω; B. 3 Ω; C. 20 Ω; D. 30 Ω

Answer 1

Answer:

D

Explanation:

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Answer 2

Given :

Length (L) = 300 m

Cross-sectional area (A) = 1 mm²

Resistivity (ρ) = 1 × 10⁻⁷ ohm. m

To Find :

Resistance of the wire

Solution :

We know,

 Resistance = ρ × $\frac{Length (L)}{Area (A)}$

Area is given in mm², we need to convert it into m²

Area (A) = 1 mm² = 1 × 10⁻⁶ m² = 10⁻⁶ m²

∴ The resistance of the wire = ρ × $\frac{L}{A}$

                                               = 1 × 10⁻⁷ × $\frac{300}{10^-^6}$

                                               = 30 Ω

Hence, the resistance of the wire is 30 Ω

∴ Option (D) is correct.