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GATE 2025 EC – Question 50

Electromagnetics · Maxwell's Equations · 2 marks · Multiple choice

An electric field of 0.01 V/m is applied along the length of a copper wire of circular cross-section with diameter 1 mm. Copper has a conductivity of $5.8\times10^7$ S/m.

The current (in Amperes, rounded off to two decimal places) flowing through the wire is ________.

  1. 0.46
  2. 1.82
  3. 0.58
  4. 1.12

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Show answer and explanation

Correct answer: (A) 0.46

Explanation

$J=\sigma E=5.8\times10^7\times0.01=5.8\times10^5$ A/m$^2$. The cross-section is $A=\pi(0.5\times10^{-3})^2=7.854\times10^{-7}$ m$^2$. So $I=JA=5.8\times10^5\times7.854\times10^{-7}\approx0.46$ A.