Question

Two conductors, one of copper and the other of iron, are connected in parallel and carry equal currents at 25°C. What proportion of current will pass through each if the temperature is raised to 100°C ? The temperature coefficients of resistance at 0°C are 0.0043/°C and 0.0063/ °C for copper and iron respectively.

Answer 1

Since the copper and iron conductors carry equal currents at 25°C, their resistances are the same at that temperature.

Let each be R ohm.

For copper, R₁₀₀ = R₁ = R [1 + 0.0043 (100 − 25)] = 1.3225 R

For iron, R₁₀₀ = R₂ = R [1 + 0.0063 (100 − 25)] = 1.4725 R

If I is the current at 100°C, then as per current divider rule, current in the copper conductor is

Hence, copper conductor will carry 52.68% of the total current and iron conductor will carry the balance i.e. 47.32%.