How long would a nickel wire with a cross-sectional area of 0.1 mm ^ 2 be required to make a rheostat with a maximum resistance of 180 ohms?
Initial data: S (cross-sectional area of nickel wire) = 0.1 mm2; R (maximum resistance of the manufactured rheostat) = 180 ohms.
Reference data: ρ (specific resistance of nickelin) = 0.4 Ohm * mm2 / m.
We calculate the required length of nickel wire from the formula for calculating the resistance: R = ρ * l / S, whence l = R * S / ρ.
Let’s make the calculation: l = 180 * 0.1 / 0.4 = 45 m.
Answer: To manufacture a rheostat, you need a 45 meter long nickelin wire.
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