The spiral is made of nichrome wire with a cross-sectional area of 0.8 mm2.

The spiral is made of nichrome wire with a cross-sectional area of 0.8 mm2. What is the length of the wire if the voltage of the coil is 22 V at a current of 0.5 A?

Initial data: S (cross-sectional area of nichrome wire) = 0.8 mm2; I (current in the coil) = 0.5 A; U (coil voltage) = 22 V.

Constants: ρ (specific resistance of nichrome at 20 ºС) = 1.1 Ohm * mm2 / m.

We express the length of the nichrome wire from which the spiral was made from the equality: U / I = R = ρ * l / S and l = U * S / (I * ρ).

Calculation: l = 22 * 0.8 / (0.5 * 1.1) = 32 m.

Answer: To make a spiral, you need a nichrome wire 32 meters long.