Question

Проводник длиной 120 см имеет сопротивление 80 Ом. Какой длины нужно взятьпроводник того же материала и той же площади поперечного сечения, чтобы егосопротивление было 12 Ом?

Answer 1

120/80=1.5  -  (нашли сопротивление на 1 см)
1.5*12=18 

Answer 2

Calculation of the Required Length

To determine the length of the conductor needed to achieve a resistance of 12 ohms, we can use the formula for resistance:

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

Given that the original conductor has a length of 120 cm and a resistance of 80 ohms, we can rearrange the formula to solve for the required length:

Required Length (L') = (Resistance (R') x Cross-sectional Area (A)) / Resistivity (ρ)

Since we want to find the length of a conductor made of the same material and with the same cross-sectional area, the resistivity (ρ) and cross-sectional area (A) will remain constant. Therefore, we can simplify the formula to:

Required Length (L') = (Resistance (R') x Length (L)) / Resistance (R)

Substituting the given values into the formula:

Required Length (L') = (12 ohms x 120 cm) / 80 ohms

Calculating the required length:

Required Length (L') = 18 cm

Therefore, a conductor of the same material and cross-sectional area would need to be 18 cm long to have a resistance of 12 ohms.

Conclusion

To achieve a resistance of 12 ohms, a conductor of the same material and cross-sectional area should be 18 cm long.