In spot welding, if the current is doubled, the heat is:

In spot welding, if the current is doubled, the heat is:

• A. Doubled
• B. Quadrupled
• C. Tripled
• D. Increased by 50%

Answer: (B)

In spot welding, the heat produced is due to resistive heating, which follows Q ∝ I^2 R t (the energy depends on current squared, multiplied by the contact resistance and weld time). If the current is doubled while resistance and time stay the same, the heat becomes (2I)^2 R t = 4 I^2 R t, which is four times the original amount. So the heat is quadrupled under those same conditions. If resistance or time change, the amount could differ, but with all else equal, doubling the current yields four times the heat.

In spot welding, the heat produced is due to resistive heating, which follows Q ∝ I^2 R t (the energy depends on current squared, multiplied by the contact resistance and weld time). If the current is doubled while resistance and time stay the same, the heat becomes (2I)^2 R t = 4 I^2 R t, which is four times the original amount. So the heat is quadrupled under those same conditions. If resistance or time change, the amount could differ, but with all else equal, doubling the current yields four times the heat.