Question

Воду массой 1,5кг нагрели до температуры кипения за 5мин. Мощность электрического чайника 2кВт, КПД 84%. Какова была начальная температура воды?При прохождении электрического тока 5,5А через спираль нагревателя, изготовленную из никеля площадью поперечного сечения 0,84мм2, за 10мин выделилось 726000Дж тепла. Чему равна длина проволоки спирали.

Answer 1

1. КПД=А(полезная)/А(затраченная)•100%
А(затраченная)=А(полезная)/КПД:100=Nt:КПД:100=2000•300:0,84=714285Дж это примерно
A=Q
Q=cm(t2-t1)
T1=Q:cm-t2
T1=714285:(4200•1,5)-100=113-100=13градусов
Ответ:13градусов
2.А=I^2Rt
R=A/I^2t
R=p(удельное сопротивление)•l:S
l=RS/p
R=726000/30,25•600=40Ом
l=40•0,84/0,4=84м
Ответ:84 метра

Answer 2

Calculation of Initial Water Temperature

To calculate the initial temperature of the water, we can use the formula for heat transfer:

Q = m * c * ΔT

Where: - Q is the heat transferred (in Joules) - m is the mass of the water (in kilograms) - c is the specific heat capacity of water (approximately 4.18 J/g°C) - ΔT is the change in temperature (final temperature - initial temperature)

Given: - Mass of water (m) = 1.5 kg - Power of the electric kettle (P) = 2 kW = 2000 W - Efficiency of the electric kettle (η) = 84% = 0.84 - Time taken to heat the water (t) = 5 minutes = 300 seconds

First, let's calculate the heat transferred (Q) using the power and time:

Q = P * t

Q = 2000 W * 300 s

Q = 600,000 J

Now, let's rearrange the heat transfer formula to solve for the initial temperature (Ti):

Ti = Tf - (Q / (m * c))

We know that the final temperature (Tf) is the boiling point of water, which is 100°C.

Ti = 100°C - (600,000 J / (1.5 kg * 4.18 J/g°C))

Ti = 100°C - (600,000 J / (1500 g * 4.18 J/g°C))

Ti = 100°C - (400 J/g°C)

Ti = 100°C - 0.27°C

Ti ≈ 99.73°C

Therefore, the initial temperature of the water was approximately 99.73°C.