The GATE Grind

GATE 2024 MT – Question 21

Mineral Processing and Extractive Metallurgy · Non-ferrous extraction · 1 mark · Multiple choice

Which statement about industrial aluminium production from pure dry alumina by Hall–Héroult electrolytic reduction is correct?

  1. Cell is operated at a high voltage (220 to 240 V) with a very low current density.
  2. Cell is operated at a low voltage (5 to 7 V) with a very low current density.
  3. Cell is operated at a high voltage (220 to 240 V) with a very high current density.
  4. Cell is operated at a low voltage (5 to 7 V) with a very high current density.

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Show answer and explanation

Correct answer: (D) Cell is operated at a low voltage (5 to 7 V) with a very high current density.

Explanation

Aluminium electrowinning operates at a low voltage per cell, roughly a few volts, while passing very large current to obtain an industrial production rate.

Hence **low voltage and very high current density, D**, rather than mains-level voltage and low current.