GATE 2020 ME (ME1) – Question 54

Machining and Machine Tool Operations · Abrasive and non-traditional machining processes · 2 marks · Numerical answer

A steel part of surface area 125 cm² is chrome-coated using chromium acid sulphate electrolyte. Current is $I=12+0.2t$ amperes, with t in minutes. Plating lasts 20 minutes. Cathode efficiency is 15% and plating constant is $2.50\times10^{-2}$ mm³/(A·s). Find coating thickness (μm), to one decimal.

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Correct answer: 0 to 0

Explanation

Charge is $60\int_0^{20}(12+0.2t)dt=16800$ A·s. Deposited volume is 0.15×0.025×16800=63 mm³. Area125 cm²=12500 mm², so thickness=63/12500=0.00504 mm=**5.0 μm**. The appended key reads 0 to 0, which conflicts with the printed units and data.