A heater coil connected to a 220 V ha a resistance of 150Ω . How long will it take for this coil to heat 1 kg of water from 20^o C to 60^o C, assuming that all the heat is taken up by the water?

Heat produced by coil = . t = . t (where t = time period) Heat required by water = m. s. θ Where m = mass of water, s = specific heat of water = 4180 joules/kg. and θ is increase in temperature = 60 – 20 = 40. Equating the heat produced and heat required. . t = 1 × 4180 × 40 ⇒ = 518 seconds. (Time taken to heat water up to 60° C)