Question

Электрический кипятильник с КПД 80% изготовлен из нихромовой проволоки сечением 0,84 мм2 и включён в сеть с напряжением 220 В. За 20 минут с его помощью было нагрето 4 л воды от 10 оС до 90 оС. Какова длина проволоки, из которой был изготовлен кипятильник? Ответ укажите в метрах ПОЖАЛУЙСТА С ОБЪЯСНЕНИЯМИ!

Answer 1

Дано КПД=80%        S=0,84 мм2    U=220 В    t=1200 с   V=4л    t1=10C   t2=90C
L- ?

КПД=Qп*100%/Qз
Qз*0,8=Qп
Qз=U^2*t/R   - затраченное тепло
Qп=с*m*(t2-t1)     m=p1*V=1000*4*10^-3=4 кг ( воды)

R=0,8*U^2*t/c*m*(t2-t1)
где R=p*L/S
L=0.8*U^2*t*S/p*c*m*(t2-t1)=0,8*220^2*1200*0,84/1,1*4200*4*80=69 м
В физике ошибок нет вычисления проверяем САМИ

Answer 2

Calculation of the Length of the Wire

To calculate the length of the wire used to make the electric kettle, we can use the formula for power:

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

The power of the kettle can be calculated using the efficiency (η) and the heat capacity of water (C):

Power (P) = Efficiency (η) * Heat Capacity (C) * Mass of Water (m) * Temperature Change (ΔT) / Time (t)

Given that the efficiency (η) is 80%, the heat capacity of water (C) is 4.18 J/g°C, the mass of water (m) is 4000 g, the temperature change (ΔT) is 90°C - 10°C = 80°C, and the time (t) is 20 minutes = 1200 seconds, we can calculate the power (P) of the kettle.

Power (P) = 0.8 * 4.18 * 4000 * 80 / 1200

Let's calculate the power:

P = 0.8 * 4.18 * 4000 * 80 / 1200 = 223.73333 Watts

Now, we can calculate the current (I) using Ohm's Law:

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

Given that the voltage (V) is 220 V, we can calculate the current (I):

I = 223.73333 / 220 = 1.017879 Amps

To find the length of the wire, we need to know the resistivity of the wire material. Unfortunately, the provided information does not include the resistivity of the nichrome wire used in the kettle. Therefore, we cannot calculate the exact length of the wire without this information.

Please provide the resistivity of the nichrome wire, and I will be able to calculate the length of the wire used in the kettle.