Two different pairs of sheets of same material are welded by resistance-spot welding. In one pair, the average radius 'r' of each spherical bridge is 0.2 mm and the number of bridges per cm2 (n) is 25. In another pair, the number of bridges per cm2 is 50 with the same ‘r’ of bridge. The contact resistance Rc per unit area is given by Rc = 0.85 (ρ / npr) where ‘ρ’ is the resistivity of metal. If the voltage applied is 5 volts and the resistivity of metal is 2 x 10-5 ohm-cm. The rate of heat generated per cm2 in each case.