Question

Какую массу m нефти нужно сжечь на тепловой электростанции, чтобы по телевизору мощностью P=250 Вт посмотреть фильм продолжительностью t=1,5 часа? КПД электростанции η=35%. Удельная теплота сгорания нефти q=44 МДж/кг. Ответ выразить в г, округлив до целых.

Answer 1

Переведем время (часы - в секунды):
t = 1,5*3600 = 5 400 c
1)
Найдем энергию, необходимую для телевизора:
Q₁ = P*t = 250*5400 = 1 350 000 Дж или 1,35 МДж

2) 
Энергия, выделившаяся при сгорании нефти:
Q₂ = Q₁ / η = 1,35/0,35 = 3,86 МДж
3)
Ну а теперь можно определить массу нефти:
Q₂ = q*m
m = Q₂ / q = 3,86 / 44 = 0,088 кг    или    надо сжечь 88 грамм нефти!!!

Answer 2

Calculation of the Mass of Oil Required

To calculate the mass of oil required to watch a movie on a television with a power of 250 W for a duration of 1.5 hours, we need to consider the efficiency of the power plant and the specific heat of combustion of oil.

Given: - Power of the television (P) = 250 W - Duration of the movie (t) = 1.5 hours - Efficiency of the power plant (η) = 35% - Specific heat of combustion of oil (q) = 44 MJ/kg

To calculate the mass of oil required, we can use the formula:

Mass of oil (m) = (Energy consumed by the television) / (Specific heat of combustion of oil)

The energy consumed by the television can be calculated using the formula:

Energy consumed = Power × Time

Substituting the given values:

Energy consumed = 250 W × 1.5 hours

To convert hours to seconds, we multiply by 3600 (1 hour = 3600 seconds):

Energy consumed = 250 W × 1.5 hours × 3600 seconds/hour

Now, let's calculate the mass of oil required.

Calculation Steps:

1. Calculate the energy consumed by the television: - Energy consumed = 250 W × 1.5 hours × 3600 seconds/hour

2. Calculate the mass of oil required: - Mass of oil (m) = Energy consumed / Specific heat of combustion of oil

Let's perform the calculations.

Calculation:

1. Calculate the energy consumed by the television: - Energy consumed = 250 W × 1.5 hours × 3600 seconds/hour - Energy consumed = 1,350,000 J

2. Calculate the mass of oil required: - Mass of oil (m) = Energy consumed / Specific heat of combustion of oil - Mass of oil (m) = 1,350,000 J / 44 MJ/kg

Converting megajoules (MJ) to joules (J): - 1 MJ = 1,000,000 J

- Mass of oil (m) = 1,350,000 J / (44 × 1,000,000 J/kg) - Mass of oil (m) = 0.0307 kg

To express the answer in grams (g), we multiply by 1000: - Mass of oil (m) = 0.0307 kg × 1000 g/kg - Mass of oil (m) = 30.7 g

Rounding the answer to the nearest whole number: - Mass of oil (m) ≈ 31 g

Therefore, approximately 31 grams of oil would need to be burned on the thermal power plant to watch a movie on a television with a power of 250 W for a duration of 1.5 hours, assuming an efficiency of 35% and a specific heat of combustion of oil of 44 MJ/kg.