A coil of insulated copper wire conducts a current of 0.05 A at a voltage of 8.5 V

A coil of insulated copper wire conducts a current of 0.05 A at a voltage of 8.5 V. What is the length of a wire in a coil if its cross-section is 0.5 mm2.

Task data: I (current in a coil of insulated copper wire) = 0.05 A; U (voltage) = 8.5 V; S (cross-sectional area) = 0.5 mm2.

Reference values: ρ (electrical resistivity of copper at 20 ºС) = 1.7 * 10-2 Ohm * mm2 / m.

We express the length of the insulated copper wire in the coil from the equality: ρ * l / S = R = U / I, whence l = U * S / (I * ρ).

Let’s perform the calculation: l = 8.5 * 0.5 / (0.05 * 1.7 * 10-2) = 5000 m.

Answer: The length of a coil of insulated copper wire is 5000 m.