Question
Current is allowed to flow in a metallic wire at a constant potential difference. When the wire becomes hot, cold water is poured on half of its portion. By doing so, its other half portion becomes still more hot. Explain its reason.
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Answer
When cold water is poured on half the wire, the resistance of this portion decreases, and hence the current $\text{I}=\frac{\text{V}}{\text{R}}$ in whole wire increases and so the other half portion becomes still more hot.
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