GATE 2024 MT – Question 65
Arc welding has actual heat input 200 J mm$^{-3}$, current 200 A, voltage 20 V, weld cross-sectional area 2 mm$^2$, and heat-transfer efficiency 0.9. Welding velocity is ______ mm s$^{-1}$ (nearest integer).
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Correct answer: 9 to 9
Explanation
Useful heat power is $\eta VI=0.9(20)(200)=3600$ J/s.
At speed $v$, the weld volume rate is $Av=2v$ mm$^3$/s.
Heat per unit volume is therefore $3600/(2v)=200$ J/mm$^3$.
Solving gives **$v=9$ mm/s**.