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An electric heater supplies heat to a system at a rate of 100 W. If the system performs work at a rate of 75 J/s, then the rate at which internal energy increases will be:

Asked in NEET 2026 · First Law and Sign Convention

• (1) 125 W
• (2) 75 W
• (3) 100 W
• (4) 25 W

Step-by-step solution

Why the other options are wrong

• (1) No single slip gives 125 W; the internal energy cannot rise faster than the 100 W of heat being supplied while the system is also doing work.
• (2) This is the rate at which the system does work, not the rate at which its internal energy rises.
• (3) This is the heat input; it would be the answer only if the system did no work.

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