Question

На электроплитке мощностью 1672 Вт растопили 372 г льда с начальной температурой −14 °С. Полученную воду довели до кипения, причем 54 г её обратилось в пар. Процесс нагревания длился 41 мин. Найди КПД плитки? (Удельная теплота плавления льда λ =330000 Дж/кг, удельная теплота парообразования воды L =2260000 Дж/кг, удельная теплоёмкость льда с1 =2100 Дж/кг·°С и воды с2 =4200 Дж/кг·°С). (Ответ округли до сотых). ПОМОГИТЕ ПОЖАЛУЙСТА! ДАЮ 30 БАЛЛОВ!

Answer 1

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Answer 2

Calculation of Heat Energy

To find the efficiency (КПД) of the electric stove, we need to calculate the heat energy supplied by the stove and the heat energy used to melt the ice and convert it into steam.

The heat energy supplied by the stove can be calculated using the formula:

Q1 = P × t

Where: - Q1 is the heat energy supplied by the stove, - P is the power of the stove (1672 W), - t is the time taken to heat the ice (41 minutes).

Substituting the given values:

Q1 = 1672 W × 41 min

To convert the time from minutes to seconds, we multiply by 60:

Q1 = 1672 W × 41 min × 60 s/min

Now, let's calculate the heat energy used to melt the ice and convert it into steam.

The heat energy used to melt the ice can be calculated using the formula:

Q2 = m × λ

Where: - Q2 is the heat energy used to melt the ice, - m is the mass of the ice (372 g), - λ is the specific latent heat of fusion for ice (330,000 J/kg).

Substituting the given values:

Q2 = 372 g × (1 kg / 1000 g) × 330,000 J/kg

The heat energy used to convert the water into steam can be calculated using the formula:

Q3 = m × L

Where: - Q3 is the heat energy used to convert water into steam, - m is the mass of the water that turned into steam (54 g), - L is the specific latent heat of vaporization for water (2,260,000 J/kg).

Substituting the given values:

Q3 = 54 g × (1 kg / 1000 g) × 2,260,000 J/kg

Calculation of Efficiency (КПД)

The efficiency (КПД) of the electric stove can be calculated using the formula:

КПД = (Q2 + Q3) / Q1

Substituting the calculated values of Q1, Q2, and Q3:

КПД = (Q2 + Q3) / Q1

Now, let's calculate the values of Q1, Q2, and Q3 and then substitute them into the efficiency formula.

Calculation Steps:

1. Calculate Q1: - Q1 = 1672 W × 41 min × 60 s/min

2. Calculate Q2: - Q2 = 372 g × (1 kg / 1000 g) × 330,000 J/kg

3. Calculate Q3: - Q3 = 54 g × (1 kg / 1000 g) × 2,260,000 J/kg

4. Calculate КПД: - КПД = (Q2 + Q3) / Q1

Let's calculate the values step by step:

1. Calculate Q1: - Q1 = 1672 W × 41 min × 60 s/min - Q1 = 1672 W × 2460 s - Q1 = 4,112,320 J

2. Calculate Q2: - Q2 = 372 g × (1 kg / 1000 g) × 330,000 J/kg - Q2 = 122,760 J

3. Calculate Q3: - Q3 = 54 g × (1 kg / 1000 g) × 2,260,000 J/kg - Q3 = 122,040 J

4. Calculate КПД: - КПД = (Q2 + Q3) / Q1 - КПД = (122,760 J + 122,040 J) / 4,112,320 J - КПД ≈ 0.0595

Therefore, the efficiency (КПД) of the electric stove is approximately 0.0595 or 5.95%.

Please note that the efficiency is rounded to the hundredths place as requested.