Question

Определиить сопротивление медных проводов телефонной линии длиной 28,5 км и лиаметром провода 4мм при темпиратуре 20С

Answer 1

Нам потребуется удельное сопротивление меди при 20 гр:

p = 0,017 Ом мм^2/м

а также площадь поперечного сечения в мм^2:

S = Пr^2 = 4П мм^2.    Тогда сопротивление провода:

R = pL/S = 0,017*28500/(4*3,14) = 38,6 Ом.

Ответ: 38,6 Ом

Answer 2

Calculating Resistance of Copper Telephone Line

To calculate the resistance of the copper telephone line, we can use the formula:

Resistance (R) = (ρ * L) / A

Where: - ρ = resistivity of copper (1.68 x 10^-8 ohm*m) - L = length of the wire (28.5 km) - A = cross-sectional area of the wire (π * r^2)

Given: - Length (L) = 28.5 km - Diameter (d) = 4 mm - Temperature (T) = 20°C

First, we need to convert the diameter to radius and then calculate the cross-sectional area (A).

Calculating Cross-Sectional Area (A)

The radius (r) can be calculated as half of the diameter.

r = d / 2 = 4 mm / 2 = 2 mm = 0.002 m

Now, we can calculate the cross-sectional area (A) using the formula:

A = π * r^2

A = 3.14 * (0.002 m)^2 = 3.14 * 4 x 10^-6 m^2 = 1.256 x 10^-5 m^2

Calculating Resistance (R)

Now, we can calculate the resistance (R) using the formula:

R = (ρ * L) / A

R = (1.68 x 10^-8 ohm*m * 28,500 m) / 1.256 x 10^-5 m^2

R ≈ 0.0378 ohms

So, the resistance of the copper telephone line with a length of 28.5 km and a diameter of 4 mm at a temperature of 20°C is approximately 0.0378 ohms.