# An electric current flows through an iron conductor with a length of 120 cm and a cross-sectional area of 0.2 mm2

**An electric current flows through an iron conductor with a length of 120 cm and a cross-sectional area of 0.2 mm2. The voltage at the ends of the conductor is 0.12 V. What is the current in the conductor? (electrical resistivity of iron = 0.1 ohm mm 2 / m) How much heat is needed to heat water weighing 500 grams at 85 degrees Celsius?**

1) Given: l (length) = 120 cm = 1.2 m; S (conductor section) = 0.2 mm2; U (voltage) = 0.12 V; ρ (specific electrical resistance) = 0.1 Ohm * mm2 / m.

Let us express the current strength from the equality: ρ * l / S = R = U / I, whence I = U * S / (ρ * l).

Calculation: I = 0.12 * 0.2 / (0.1 * 1.2) = 0.2 A.

2) Given: m (mass) = 500 g = 0.5 kg; Δt (temperature change) = 85 ºС; Sv (specific heat capacity) = 4200 J / (kg * K).

Formula: Q = Sv * m * Δt.

Calculation: Q = 4200 * 0.5 * 85 = 178 500 J = 178.5 kJ.