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Heat transfer methods differ fundamentally in whether they require a medium and whether particles physically move. Option A (Conduction) is incorrect — conduction requires a medium but the particles do NOT physically move from their positions. In conduction, energy passes from particle to particle through vibrations, like a chain of balls passing a push without the balls themselves moving positions. Option B (Radiation) is incorrect — radiation does NOT require a medium and involves no movement of particles. Radiation travels as electromagnetic waves through vacuum. Option C (Convection) is CORRECT — convection requires a medium AND involves the actual physical movement of heated particles from one place to another. When a liquid or gas is heated, the heated portion becomes less dense, rises, the cooler denser portion sinks, and a convection current is established. The particles themselves physically move, carrying thermal energy with them. The image states: संवहन — गैसों व द्रवों में ऊष्मा का संचरण, पृथ्वी का वायुमंडल गर्म होना संवहन विधि से। Option D (All three methods) is incorrect — only convection satisfies both conditions (needs medium AND particles move). Conduction needs medium but no particle movement. Radiation needs no medium and no particle movement. For exams: Convection = medium needed + particle movement.
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Common questions and clear answers for this topic.
Heat is a form of energy that transfers between objects or systems due to a temperature difference, moving from a hotter body to a cooler one until thermal equilibrium is reached.
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