From the battery of a pocket lamp, the boy ran iron wires to one of the two identical bulbs, and copper wires to the other.

From the battery of a pocket lamp, the boy ran iron wires to one of the two identical bulbs, and copper wires to the other. Which light bulb will have a brighter filament if the length and cross-sectional area of the wires are the same?

Since the resistivity of iron is greater than the resistivity of copper, more electrical energy is lost on iron wires at the same time than on copper. Therefore, the filament of a light bulb in a chain with copper wires will glow brighter.

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