Question

С помощью электронагревателя необходимо вскипятить m = 2 кг воды, взятой при температуре t1 = 12 Сила тока в нагревателе равна I = 8 A напряжение в сети U=220 В КПД нагревателя равен n = 40% Удельная теплоёмкость воды равна c = 4200 дж / (кг C ) Температура кипения воды равна t2 = 100. Определите количество теплоты, которое необходимо передать воде, чтобы нагреть ее до кипения. Ответ выразить в КДЖ округлив до десятых. Сколько времени t потребуется, чтобы довести воду до кипения. Ответ выразить в мин округлив до десятых.

Answer 1

Ответ:

739,2 кДж

формула t=c*m*(t2-t1) : I*U*n

17.5 минут

Объяснение:

тот же вопрос на фоксе

Answer 2

Calculation of the Heat Required to Heat the Water to its Boiling Point

To determine the amount of heat required to heat the water to its boiling point, we can use the formula:

Q = m * c * ΔT

Where: - Q is the heat energy (in joules) - m is the mass of the water (in kilograms) - c is the specific heat capacity of water (in joules per kilogram per degree Celsius) - ΔT is the change in temperature (in degrees Celsius)

Given: - Mass of water, m = 2 kg - Initial temperature, t1 = 12°C - Specific heat capacity of water, c = 4200 J/(kg·°C) - Boiling point temperature, t2 = 100°C

We can calculate the change in temperature, ΔT, using the formula:

ΔT = t2 - t1

Substituting the given values:

ΔT = 100°C - 12°C = 88°C

Now, we can calculate the heat energy, Q, using the formula:

Q = m * c * ΔT

Substituting the given values:

Q = 2 kg * 4200 J/(kg·°C) * 88°C = 739,200 J

Therefore, the amount of heat required to heat the water to its boiling point is 739,200 joules (J).

Calculation of the Time Required to Bring the Water to its Boiling Point

To determine the time required to bring the water to its boiling point, we can use the formula:

Q = P * t

Where: - Q is the heat energy (in joules) - P is the power (in watts) - t is the time (in seconds)

Given: - Power, P = U * I - Voltage, U = 220 V - Current, I = 8 A - Heat energy, Q = 739,200 J - Efficiency, n = 40% (or 0.4)

We can calculate the power, P, using the formula:

P = U * I

Substituting the given values:

P = 220 V * 8 A = 1760 W

Since the efficiency, n, is given as 40%, we can calculate the actual power used, P_actual, by multiplying it with the efficiency:

P_actual = P * n = 1760 W * 0.4 = 704 W

Now, we can calculate the time, t, using the formula:

Q = P_actual * t

Rearranging the formula to solve for t:

t = Q / P_actual

Substituting the given values:

t = 739,200 J / 704 W = 1050 seconds

Converting the time to minutes:

t = 1050 seconds * (1 minute / 60 seconds) = 17.5 minutes

Therefore, it will take approximately 17.5 minutes to bring the water to its boiling point.