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For spot welding of two steel sheets (base metal) each of 3 mm thickness, welding current of 10000 A is applied for 0.2 s. The heat dissipated to the base metal is 1000 J. Assuming that the heat required for melting 1 mm³ volume of steel is 20 J and interfacial contact resistance between sheets is 0.0002 ohms, the volume (in mm³) of weld nugget is.
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- 180mm³
- 50mm³
- 150mm³
- 60mm³
Correct Option: C
Heat required = 20 J/mm³
I = 10000 A
R = 0.0002Ω
t = 0.2 sec
H = I² R t
= (10000)² × 0.0002 × 0.2 = 4000 Joules
Heat Required to melt the nugget
= 4000 – 1000 = 3000 Joules
Volume of Nugget = 3000/3 = 150mm³
