Question

Задача:Электрическая печь потребляет мощность 800 кВт при напряжении 220 В. Обмотка печи сделана из никелиновой проволоки длиной 72 м. найти сечение проволоки . p=0,4 Ом*мм2/м. Заранее спасибо)

Answer 1

P=IU=U^2:R

R=pl:S

P=(U^2*S):(pl)

S=(Ppl):(U^2)

Answer 2

Calculation of Wire Cross-Sectional Area

To find the cross-sectional area of the nickel-chromium wire used in the electric stove, we can use the formula:

Resistance (R) = Resistivity (ρ) x Length (L) / Cross-Sectional Area (A)

Given: - Power (P) = 800 kW = 800,000 W - Voltage (V) = 220 V - Length of wire (L) = 72 m - Resistivity (ρ) = 0.4 Ω*mm²/m

First, let's calculate the current (I) flowing through the wire using Ohm's Law:

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

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

Substituting the given values:

Current (I) = 800,000 W / 220 V

Now, let's calculate the resistance (R) of the wire using Ohm's Law:

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

Substituting the given values:

Resistance (R) = 220 V / Current (I)

Next, we can rearrange the formula for resistance to solve for the cross-sectional area (A):

Cross-Sectional Area (A) = Resistivity (ρ) x Length (L) / Resistance (R)

Substituting the given values:

Cross-Sectional Area (A) = (0.4 Ω*mm²/m) x 72 m / Resistance (R)

To find the value of resistance (R), we can use the previously calculated current (I) and voltage (V):

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

Substituting the given values:

Resistance (R) = 220 V / Current (I)

Now, we can substitute the value of resistance (R) into the formula for cross-sectional area (A):

Cross-Sectional Area (A) = (0.4 Ω*mm²/m) x 72 m / (220 V / Current (I))

Finally, we can substitute the value of current (I) into the equation:

Cross-Sectional Area (A) = (0.4 Ω*mm²/m) x 72 m / (220 V / (800,000 W / 220 V))

Simplifying the equation:

Cross-Sectional Area (A) = (0.4 Ω*mm²/m) x 72 m / (220 V / (800,000 W / 220 V))

Cross-Sectional Area (A) ≈ 0.017 mm²

Therefore, the cross-sectional area of the nickel-chromium wire used in the electric stove is approximately 0.017 mm².

Please note that the calculation assumes a uniform cross-sectional area for the wire and does not take into account any variations or irregularities in the wire's shape or composition.

Conclusion

The cross-sectional area of the nickel-chromium wire used in the electric stove is approximately 0.017 mm².