Question

В электрочайник налили 0,75 л воды и включили его в сеть через 20 минут после включения вся вода выкипела мощность нагревателя 2кВт КПД нагревателя 80% какова была начальная температура воды​

Answer 1

Ответ:

81%

Объяснение:

Рассчитываем количество энергии необходимое для испарения воды:

Q = V*po*(t-t0)*C+V*L=0.75*1*72*4200+0.75*2300000=1951800Дж.

Tч = Q/N=1951800/2000=975.9c=976c.

n(кпд) = Tч / T=976/60*20=976/1200=81%.

Answer 2

V=0.75 л=0,75*10^-3 м³

ρ=1000 кг/м³

t=20 мин=1200 с

N=2*10³ Вт

КПД=80%

L=2300*10³ Дж/кг

c=4200 Дж/кг°С

t*=100°C

t0-?

КПД=(Qп/Qз)*100%

Qп=cm(t-t0)+Lm (сначала вода нагревалась до 100°, а потом шло образование пара, в следствии чего вся вода выкипела)

m=Vρ

Qп=cVρ(t*-t0)+LVρ

Qз=А=Nt

Дальше действия на листке

Answer 3

Calculation of Initial Water Temperature

To calculate the initial temperature of the water in the kettle, we can use the formula:

Q = m * c * ΔT

Where: - Q is the heat energy transferred to the water (in Joules) - m is the mass of the water (in kilograms) - c is the specific heat capacity of water (approximately 4.18 J/g°C) - ΔT is the change in temperature (in °C)

In this case, we know the following information: - The power of the heater is 2 kW (or 2000 W), which means it transfers 2000 Joules of energy per second. - The efficiency of the heater is 80%, which means 80% of the energy is actually transferred to the water.

Let's assume the initial temperature of the water is T°C.

After 20 minutes (or 1200 seconds), all the water has boiled, which means it has reached 100°C.

Using the formula above, we can calculate the mass of the water:

Q = m * c * ΔT

2000 J/s * 0.8 * 1200 s = m * 4.18 J/g°C * (100°C - T°C)

Simplifying the equation:

960000 J = m * 4.18 J/g°C * (100°C - T°C)

Now, let's convert the mass of water from grams to kilograms:

960000 J = (m/1000) kg * 4.18 J/g°C * (100°C - T°C)

Simplifying further:

960000 J = m * 4.18 J/°C * (100°C - T°C)

960000 J = m * 418 J/°C * (100°C - T°C)

Dividing both sides of the equation by 418 J/°C:

2296.65 kg = m * (100°C - T°C)

Now, we can solve for the initial temperature T:

T°C = 100°C - (2296.65 kg / m)

To find the value of m, we need to know the density of water. However, the given information does not provide the density of water or the volume of water in the kettle.

Without the density or volume information, it is not possible to calculate the initial temperature of the water accurately.

Please provide additional information if available, such as the density or volume of water, to calculate the initial temperature.