An electrochemical machining (ECM) is to be used to cut a through hole into a 12 mm thick aluminium plate. The hole has a rectangular cross- section, 10 mm 30 mm. The ECM operation will be accomplished in 2 minutes, with efficiency of 90%. Assuming specific removal rate for aluminium as 3.44 10 2 mm / (A s), the current (in A) required is _____ (correct to two decimal places).

An electrochemical machining (ECM) is to be used to cut a through hole

1.	An electrochemical machining (ECM) is to be used to cut a through hole into a 12 mm thick aluminium plate. The hole has a rectangular cross- section, 10 mm 30 mm. The ECM operation will be accomplished in 2 minutes, with efficiency of 90%. Assuming specific removal rate for aluminium as 3.44 10 2 mm / (A s), the current (in A) required is _____ (correct to two decimal places).
A.	988
B.	962
C.	968.992
D.	868
Answer» D. 868

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