How long does it take to heat 500 g of water in a glass from 20 (degrees) to a boil using a 500 W electric boiler?

N = 500 W.

m = 500 g = 0.5 kg.

C = 4200 J / kg * ° С.

t1 = 20 ° C.

t2 = 100 ° C.

T -?

The amount of heat Q that is released in an electric boiler is expressed by the formula: Q = N * T, where N is the power of the boiler, T is the operating time of the boiler.

The amount of heat Q, which is necessary for heating water, is expressed by the formula: Q = C * m * (t2 – t1), where C is the specific heat capacity of water, m is the mass of water that was heated, t2, t1 are the final and initial water temperatures.

Since the water was heated to boiling, the boiling point of water is t2 = 100 ° C.

N * T = C * m * (t2 – t1).

We express the heating time of water by the formula: T = C * m * (t2 – t1) / N.

T = 4200 J / kg * ° C * 0.5 kg * (100 ° C – 20 ° C) / 500 W = 336 s.

Answer: it takes time T = 336 s to heat water to boiling.