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Spot welding of two 1 mm thick sheets of steel (density = 8000 kg/m³) is carried out successfully by passing a certain amount of current for 0.1 second through the electrodes. The resultant weld nugget formed is 5 mm in diameter and 1.5 mm thick. If the latent heat of fusion of steel is 1400 kJ/kg and the effective resistance in the welding operation is 200 μ-ohms, the current passing through the electrodes is approximately
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- 1480 A
- 3300 A
- 4060 A
- 9400 A
Correct Option: C
ρ = 8000 kJ/m³
t = 0.1 sec dn = 5 mm
hn = 1.5 mm
LH = 1400 kJ/kg R = 200 µΩ
I =?
mass = 8000 × 10-9 × (π/4) 5² × 1.5
= 2.356 × 10-4kg.
Heat = 1400 × 8000 × 2.356 × 10-4
= 329.8 Joules
Heat = I² × 200 × 10-6 × 0.1
I = 4060 Amp.
