Question

Помогите!!!!!!!!!!!! Заранее благодарю. Вычислите КПД спиртовки, если для нагрева 1л воды от +20 до +70^0C были сожжены 40г спирта.

Answer 1

Дано:
m(вода)=1 л
m(спирт)=0.04 кг
t0=20°C
t=70°C
q(спирт)=27*10^6 МДж/кг
c(вода)=4200 Дж/кг*°C
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КПД-?
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Решение:

КПД= х
КПД=((mct(d))/mq)*100%
x=((1*4200*(70-20))/0.04*27*10^6)*100%
x=0.1944*100%=19.44%
Ответ: КПД=19.44%

Answer 2

Calculating the Efficiency of the Alcohol Burner

To calculate the efficiency of the alcohol burner in heating 1 liter of water from 20°C to 70°C using 40g of alcohol, we can use the formula for efficiency:

Efficiency (%) = (useful energy output / energy input) x 100

In this case, the useful energy output is the energy transferred to the water to raise its temperature, and the energy input is the energy released by burning the alcohol.

Calculating the Energy Input

The energy released by burning the alcohol can be calculated using the formula:

Energy = mass of fuel burned x heat of combustion

The heat of combustion for alcohol is approximately 26.8 kJ/g.

So, the energy input from burning 40g of alcohol can be calculated as:

Energy input = 40g x 26.8 kJ/g

Calculating the Useful Energy Output

The useful energy output is the energy transferred to the water to raise its temperature. This can be calculated using the formula:

Energy = mass of water x specific heat capacity x temperature change

The specific heat capacity of water is approximately 4.18 J/g°C.

So, the energy required to raise 1 liter (1000g) of water from 20°C to 70°C can be calculated as:

Energy output = 1000g x 4.18 J/g°C x (70°C - 20°C)

Calculating Efficiency

Now that we have calculated the energy input and the useful energy output, we can use the efficiency formula to find the efficiency of the alcohol burner in this scenario.

Efficiency (%) = (useful energy output / energy input) x 100

Let's calculate the values and find the efficiency.