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When ends of a wire are connected to a battery, initially the current is slightly larger ,but soon it decrease become steady at lower value, why ? ?

When ends of a wire are connected to a battery, initially the current is slightly larger ,but soon it decrease become steady at lower value, why ? ?

Grade:12

2 Answers

Saurabh Koranglekar
askIITians Faculty 10335 Points
3 years ago
The reason is that wire has resistance, and when initially connected, the wire is at room temperature, thus has some given low resistance per length. When current flows, the wire heats up from the current. This increases the wire temperature, and so the wire resistance increases, decreasing current flow. This continues until an equilibrium is reached where the heat generated is dissipated at a steady rate into surrounding air. As you might expect, if the wire is covered with insulation, the wire will be at a higher temperature when equilibrium is reached than if the wire was bare. This actually figures in to building electrical codes- for example, the inspector won’t allow romex (double insulation clad wire) be installed in metal conduit because of the heat rise; only separate insulated wires are allowed in metallic conduit.
Vikas TU
14149 Points
3 years ago
When the ends of a wire are connected to a battery, initially the current is slightly larger, but soon it decreases slowly and becomes steady at a lower value although the EMF of the battery remains unchanged.

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