GATE 2024 PI – Question 52
Mild-steel butt joints are arc welded at 85% heat-transfer efficiency, ignoring other losses. First weld: 30 V,180 A,6 mm/s. Second uses identical plates, same voltage and 8 mm/s. For equal heat input per weld length, find second current (integer A).
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Correct answer: 240 to 240
Explanation
Heat input per length is $\eta VI/v$. Equal efficiency and voltage cancel, leaving $I_2/v_2=I_1/v_1$. Hence $I_2=180(8/6)=\mathbf{240}$ A.