Matter - Heat and Energy

Let R be the resistance of the heating coil.
Energy delivered by the coil to water in 1 sec. = V^2/R
hence, V^2/R = mL ---------------------- (1)
where L is the latent heat of vapourization of water

Now, new voltage = 4V
hence, (4V)^2/R = m'L -------------------- (2)
where m' is the new mass vapourized per second

(2)/(1): 16 = m'/m
i.e. m' = 16m

The answer is therefore option D

I don't know.問任何一個物理科學家,都懂得教導你^^