# What is the cross-sectional area of a 6 m long manganin wire if, with a voltage at its ends of 1.5 V

September 22, 2021 | education

| **What is the cross-sectional area of a 6 m long manganin wire if, with a voltage at its ends of 1.5 V, the current in it is 400 mA? Resistivity of manganin 0.43 Ohm Mm2 / m**

To calculate the value of the cross-sectional area of the specified manganin wire, it is necessary to use the equality: U / I = R = ρm * l / S, whence we express: S = ρm * l * I / U.

Variables and constants: ρm – electrical resistivity of manganin (by condition ρm = 0.43 Ohm * mm2 / m); l – wire length (l = 6 m); I – current (I = 400 mA = 0.4 A); U is the effective voltage (U = 1.5 V).

Calculation: S = ρm * l * I / U = 0.43 * 6 * 0.4 / 1.5 = 0.688 mm2.

Answer: The cross-sectional area of the specified manganin wire is 0.688 mm2.