Question

Электрический нагреватель за 20 мин доводит до кипения 3 л воды, взятой при температуре 10С. Напряжение в сети 220 В, а потребляемый ток – 7 А. Какая часть энергии при этом передаётся окружающей среде?

Answer 1

Количество теплоты необходимое на нагрев воды до температуры кипения:
Q=cm(t2-t1)=4200*3*(100-10)=1.134*10⁶Дж
Количество теплоты выделяемое нагревателем (закон Джоуля-Ленца)
Q=UIt=7*220*20*60=1.848*10⁶Дж
Окружающей среде передается (1.848*10⁶Дж-1.134*10⁶Дж)/1.848*10⁶Дж=0,39
39%
Ответ 39%

Answer 2

Calculating Energy Transfer to the Surroundings

To calculate the energy transferred to the surroundings when an electric heater brings 3 liters of water from 10°C to boiling in 20 minutes, we can use the formula:

Q = mcΔT

Where: - Q is the energy transferred - m is the mass of the substance (in this case, water) - c is the specific heat capacity of the substance - ΔT is the change in temperature

First, we need to calculate the energy required to heat the water from 10°C to 100°C.

Calculating Energy Required to Heat Water

The specific heat capacity of water is approximately 4.18 J/g°C Given that we have 3 liters of water, which is equivalent to 3000 grams (since 1 liter of water is approximately 1000 grams), and the temperature change is from 10°C to 100°C, we can calculate the energy required:

Q = mcΔT Q = (3000g)(4.18 J/g°C)(100°C - 10°C)

This calculation will give us the energy required to raise the temperature of the water to its boiling point.

Calculating Energy Required for Phase Change

Once the water reaches 100°C, it will require additional energy to undergo a phase change from liquid to gas. This energy is known as the latent heat of vaporization.

The latent heat of vaporization of water is approximately 2260 J/g Given that we have 3000 grams of water, we can calculate the energy required for the phase change:

Q = mL Q = (3000g)(2260 J/g)

Total Energy Required

By adding the energy required to heat the water to 100°C and the energy required for the phase change, we can find the total energy required to bring 3 liters of water to a boil in 20 minutes.

Calculating Energy Consumption

With the voltage of 220V and a current of 7A, we can calculate the power consumption using the formula:

P = VI

Where: - P is the power in watts - V is the voltage in volts - I is the current in amperes

Once we have the power consumption, we can calculate the total energy consumed over 20 minutes.

Determining Energy Transferred to the Surroundings

Finally, to find the energy transferred to the surroundings, we can compare the total energy consumed by the heater with the total energy required to heat the water and cause the phase change.

Let's calculate these values.