Question

В електричний чайник налили 2 кг води при температурі 12 °С. Через який час закипить вода в чайнику,якщо сила струму в його нагрівальному елементі дорівнює 10 А, а напруга в мережі становить 220В? ККД чайника 84%.(Відповідь в секундах)​

Answer 1

Ответ: 409с

Объяснение:

Дано:

m=2кг

с=4200Дж/кг°С

t1=10°C

t2=100°C

I=10А

U=220В

η=84%

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t-?

η=Qп/Qз, где:

Qп-полезная теплота;

Qз-затраченная теплота

Qп=cm(t2-t1), где:

с-удельная теплоемкость воды;

m-масса воды;

t1 и t2- начальная и конечная темпетарура воды

Qз=UIt, где:

U-напряжение сети;

I-сила тока в нагревателе;

t-время работы нагревателя.

Отсюда:

t=cm(t2-t1)/(UIη)=4200*2*(100-10)/(220*10*0,84)=409с

Answer 2

To calculate the time it takes for the water to boil in the electric kettle, we need to consider the power of the heating element and the efficiency of the kettle.

Given: - Mass of water (m) = 2 kg - Initial temperature of water (T1) = 12 °C - Current in the heating element (I) = 10 A - Voltage in the circuit (V) = 220 V - Efficiency of the kettle (η) = 84%

Calculating the energy required to heat the water:

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

Q = mcΔT

Where: - Q is the energy in Joules - m is the mass of water in kg - c is the specific heat capacity of water (approximately 4186 J/kg°C) - ΔT is the change in temperature (final temperature - initial temperature)

Using the given values, we can calculate the energy required:

Q = (2 kg) * (4186 J/kg°C) * (100 °C - 12 °C)

Calculating the power:

The power (P) can be calculated using the formula:

P = IV

Where: - P is the power in Watts - I is the current in Amperes - V is the voltage in Volts

Using the given values, we can calculate the power:

P = (10 A) * (220 V)

Calculating the time:

The time (t) can be calculated using the formula:

t = Q / (P * η)

Where: - t is the time in seconds - Q is the energy in Joules - P is the power in Watts - η is the efficiency (expressed as a decimal)

Using the calculated values, we can calculate the time it takes for the water to boil:

t = Q / (P * η)

Now let's calculate the values and find the answer.

Calculation:

- Q = (2 kg) * (4186 J/kg°C) * (100 °C - 12 °C) = 2 * 4186 * 88 = 737,536 J - P = (10 A) * (220 V) = 2,200 W - η = 84% = 0.84

Substituting the values into the formula:

t = 737,536 J / (2,200 W * 0.84)

Calculating the result:

t ≈ 165.8 seconds

Therefore, it will take approximately 165.8 seconds for the water to boil in the electric kettle.

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