GATE 2024 PI – Question 59
ECM removes copper at constant rate 2 cm³/min. Find current (one decimal A), using melting point 1085°C, density 9 g/cm³, atomic weight 63 g/mol, dissolution valency 2, Faraday constant 96500 C/mol and Stefan–Boltzmann constant $5.67\times10^{-8}$ W/(m²·K⁴).
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Correct answer: 915.0 to 925.0
Explanation
Mass-removal rate is $2(9)/60=0.3$ g/s. Faraday’s law gives $\dot m=IM/(zF)$, so $I=0.3(2)(96500)/63=919.0476$ A, or **919.0 A**. Melting temperature and the radiation constant are irrelevant because removal is electrochemical.