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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
[ME 2005]
  • a)
    1480 A
  • b)
    3300 A
  • c)
    4060 A
  • d)
    9400 A
Correct answer is option 'C'. Can you explain this answer?
Verified Answer
Spot welding of two 1 mm thick sheets of steel (density = 8000 kg/m3) ...
ρ = 8000 kJ/m3
t = 0.1 sec dn = 5 mm
hn = 1.5 mm
LH = 1400 kJ/kg R = 200 µ Ω
I = ?

= 2.356 × 10–4kg.
Heat = 1400 × 8000 × 2.356 × 10–4
= 329.8 Joules
Heat = I2 × 200 × 10–6 × 0.1
I = 4060 Amp.
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Most Upvoted Answer
Spot welding of two 1 mm thick sheets of steel (density = 8000 kg/m3) ...
ρ = 8000 kJ/m3
t = 0.1 sec dn = 5 mm
hn = 1.5 mm
LH = 1400 kJ/kg R = 200 µ Ω
I = ?

= 2.356 × 10–4kg.
Heat = 1400 × 8000 × 2.356 × 10–4
= 329.8 Joules
Heat = I2 × 200 × 10–6 × 0.1
I = 4060 Amp.
Free Test
Community Answer
Spot welding of two 1 mm thick sheets of steel (density = 8000 kg/m3) ...
The first step is to calculate the mass of the weld nugget. We can use the formula for the volume of a cylinder to find the volume of the weld nugget:

Volume = π * r^2 * h

Where:
r = radius of the weld nugget = 5 mm / 2 = 2.5 mm = 0.0025 m
h = height of the weld nugget = 1.5 mm = 0.0015 m

Volume = π * (0.0025 m)^2 * 0.0015 m
Volume = 1.76714587e-8 m^3

Next, we can calculate the mass of the weld nugget using its volume and the density of steel:

Mass = Volume * Density
Mass = 1.76714587e-8 m^3 * 8000 kg/m^3
Mass = 0.00014137167 kg

Now, we can calculate the energy required to melt this mass of steel using the latent heat of fusion:

Energy = Mass * Latent Heat of Fusion
Energy = 0.00014137167 kg * 1400 kJ/kg
Energy = 0.19792034 kJ

Finally, we can calculate the power used in the welding operation using the energy and the time:

Power = Energy / Time
Power = 0.19792034 kJ / 0.1 s
Power = 1.9792034 kJ/s

Now, we need to calculate the current using the power and the effective resistance:

Power = Current^2 * Resistance
1.9792034 kJ/s = Current^2 * 200 Ω

Solving for Current:

Current^2 = 1.9792034 kJ/s / 200 Ω
Current^2 = 9.896017e-3 A^2

Current = sqrt(9.896017e-3 A^2)
Current = 0.0994806 A

Therefore, the current used in the welding operation is approximately 0.0995 A.
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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[ME 2005]a)1480 Ab)3300 Ac)4060 Ad)9400 ACorrect answer is option 'C'. Can you explain this answer?
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