A wire \(50 \mathrm{~cm}\) long and \(1 \mathrm{~mm}^{2}\) in cross-section carries a current of \(4 \mathrm{~A}\) when connected to a \(2 \mathrm{~V}\) battery. The resistivity of the wire is: (A) \(2 \times 10^{-7} \Omega \mathrm{m}\) (B) \(5 \times 10^{-7} \Omega \mathrm{m}\) (C) \(4 \times 10^{-6} \Omega \mathrm{m}\) (D) \(1 \times 10^{-6} \Omega \mathrm{m}\)

Short Answer

Expert verified
The resistivity of the wire is \(1\times10^{-6} \Omega m\) (Option D).

Step by step solution

01

Calculate the resistance using Ohm's law

Ohm's law states that the voltage is equal to the product of current (I) and resistance (R): \[V = IR\] We are given the current (I = 4 A) and the voltage (V = 2 V). We will use Ohm's law to find the resistance (R): \[R = \frac{V}{I} = \frac{2}{4}\]
02

Find the resistance value

By solving for R, we find its value: \[R = \frac{2}{4} = 0.5 \Omega\]
03

Use the resistance formula to find resistivity

The formula for the resistance in terms of resistivity (ρ), length (L), and cross-sectional area (A) is: \[R = \frac{\rho L}{A}\] We are given the length (L = 50 cm = 0.5 m) and cross-sectional area (A = \(1 mm^2 = 1\times10^{-6} m^2\)). We will use the observed resistance (R = 0.5 Ω) and the formula to find the resistivity (ρ): \[\rho = \frac{RA}{L} = \frac{0.5 \times 1\times10^{-6}}{0.5}\]
04

Calculate the resistivity

By solving for ρ, we find its value: \[\rho = \frac{0.5 \times 1\times10^{-6}}{0.5} = 1\times10^{-6} \Omega m\] The resistivity of the wire is therefore \(1\times10^{-6} \Omega m\), which corresponds to option (D).

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