0.5 kg of water was poured into an electric kettle at a temperature of 12C. How long will it take for the water

| May 4, 2021 | education

0.5 kg of water was poured into an electric kettle at a temperature of 12C. How long will it take for the water in the teahouse to start, if the current in its heating element is 10A, and the voltage in the network is 220V? The efficiency of the kettle is 84%.

Let’s find the amount of energy needed to heat the kettle to the boiling point: Q = m * C * (T2 – T1), where m is the mass, C is the heat capacity, T2 and T1 are the initial and final temperatures, respectively.

Q = 0.5 * 4.2 * (100 – 12) = 184.8 kJ.

Taking into account the efficiency, the energy of the heating element will be:

Q = 184.8 / 84 * 100 = 220 kJ.

Let’s turn to the power formula in the electric circuit: P = U * I, where U is the voltage, I is the current. Then the equality is true:

Q = U * I * t, where t is time.

t = Q / U * I

t = 220,000 / 220 * 10 = 1000/10 = 100 s.



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