Question

Найди соответствующую величину. Нагревателем вскипятили 1 л воды при температуре 25°С за 3 мин, включенным в сеть с напряжением 220 В. КПД нагревателя составляет 80%. (cводы = 4200 Дж/кг ∙ К) Рассчитай работу нагревателя: (до целого числа) A = кДж Определи мощность нагревателя: (до целого числа) P = кВт Рассчитай сопротивление спирали: (до целого числа) R = Ом Что произойдет с мощностью нагревателя, если в 2 раза укоротить спираль?

Answer 1

Снизу на фото...
Надеюсь помогла вам.

Answer 2

удачи!!

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Answer 3

Calculation of Work Done by the Heater

To calculate the work done by the heater, we can use the formula:

Work (W) = Energy (Q) x Efficiency (η)

The energy required to heat the water can be calculated using the formula:

Energy (Q) = mass (m) x specific heat capacity (c) x change in temperature (ΔT)

Given: - Mass of water (m) = 1 kg - Specific heat capacity of water (c) = 4200 J/kg·K - Change in temperature (ΔT) = Final temperature - Initial temperature = 100°C - 25°C = 75°C

Using the above values, we can calculate the energy (Q) required to heat the water:

Q = 1 kg x 4200 J/kg·K x 75 K = 315,000 J

Now, we can calculate the work done by the heater:

W = Q x η = 315,000 J x 0.8 = 252,000 J

Therefore, the work done by the heater is 252,000 Joules.

Calculation of Power of the Heater

Power (P) is defined as the rate at which work is done. It can be calculated using the formula:

Power (P) = Work (W) / Time (t)

Given: - Time taken (t) = 3 minutes = 180 seconds

Using the above values, we can calculate the power of the heater:

P = 252,000 J / 180 s = 1,400 W

Therefore, the power of the heater is 1,400 Watts or 1.4 kilowatts.

Calculation of Resistance of the Heating Coil

The resistance (R) of the heating coil can be calculated using Ohm's Law:

Resistance (R) = Voltage (V) / Current (I)

Given: - Voltage (V) = 220 V

To calculate the current (I), we can use the formula:

Power (P) = Voltage (V) x Current (I)

Using the above values, we can calculate the current (I):

I = P / V = 1,400 W / 220 V = 6.36 A

Now, we can calculate the resistance (R):

R = V / I = 220 V / 6.36 A = 34.59 Ω

Therefore, the resistance of the heating coil is approximately 34.59 Ohms.

Effect of Shortening the Heating Coil

If the heating coil is shortened by a factor of 2, the resistance of the coil will decrease. This is because resistance is inversely proportional to the length of the wire. As the length decreases, the resistance decreases.

The power of the heater can be calculated using the formula:

Power (P) = Voltage (V) x Current (I)

Since the voltage remains the same, if the resistance decreases, the current will increase. As a result, the power of the heater will increase.

However, it's important to note that shortening the heating coil without considering the specifications and design of the heater can lead to overheating and potential damage to the equipment. It is always recommended to consult a professional or follow the manufacturer's guidelines when making modifications to electrical devices.