Electrical heat generated = quantity of heat required to change water from liquid to vapour
I2 R t = mL
I = current = 10A, R = resistance = 2Ω, t = time = 20s, m = mass of water = 5 X 10−3kg and L = specific latent heat of vaporization.
102 x 2 x 20 = 5 X 10−3L
4000 = 5 X 10−3L
L = 40005×10−3 = 800000 ⇔ 8.0 x 105Jkg−1
