JEE Main 2026 — Jan 28, Shift 1 — Physics solution

JEE Main2026Jan 28, Shift 1Physics

Which of the following best represents the temperature versus heat supplied graph for water, in the range of $- 2 0^{\circ}$ C to $12 0^{\circ}$ C ?

Solution

Sketch the expected T-vs-heat curve in five stages:

1. Ice warming from $- 20$ to $0^{\circ}$ C: linear rise (slope $= 1/ (m c_{ice})$ ).

2. Melting at $0^{\circ}$ C: horizontal plateau of width $m L_{f}$ .

3. Water warming $0 \to 10 0^{\circ}$ C: linear rise (smaller slope since $c_{w} > c_{ice}$ ).

4. Boiling at $10 0^{\circ}$ C: horizontal plateau of width $m L_{v}$ , much longer than the melting plateau ( $L_{v} \approx 7 L_{f}$ ).

5. Steam warming $100 \to 12 0^{\circ}$ C: linear rise.

The graph showing this sequence with the correct relative plateau lengths is option (2).

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