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MP Board · Class 9 · Science · Work and EnergyThe commercial unit of electrical energy is kilowatt-hour (1 kWh). How many Joules (J) are equal to 1 kWh?

Q: The commercial unit of electrical energy is kilowatt-hour (1 kWh). How many Joules (J) are equal to 1 kWh?

Correct Option: (B) 3.6 × 10⁶ J Calculation & Explanation: 1 kWh represents the energy consumed by an appliance of 1 kilowatt power in 1 hour. $$1\text{ kWh} = 1\text{ kW} \times 1\text{ hour}$$ $$1\text{ kWh} = 1000\text{ Watts} \times 3600\text{ seconds}$$ $$1\text{ kWh} = 3,600,000\text{ Joules} = 3.6 \times 10^6\text{ J}$$ \nHence, 1 kilowatt-hour is equal to $3.6 \times 10^6\text{ Joules}$.

Step-by-Step Solution

Correct Option: (B) 3.6 × 10⁶ J

Calculation & Explanation: 1 kWh represents the energy consumed by an appliance of 1 kilowatt power in 1 hour.

$$1\text{ kWh} = 1\text{ kW} \times 1\text{ hour}$$ $$1\text{ kWh} = 1000\text{ Watts} \times 3600\text{ seconds}$$ $$1\text{ kWh} = 3,600,000\text{ Joules} = 3.6 \times 10^6\text{ J}$$ \nHence, 1 kilowatt-hour is equal to $3.6 \times 10^6\text{ Joules}$.

Detailed Options Breakdown

Option : 3.6 × 10⁵ J

Incorrect choice. This distractor represents a common misunderstanding of the core principles of Work and Energy.

Option 1: 3.6 × 10⁶ J (Correct Answer)

Correct choice. Refer to the step-by-step verified solution guidelines above for details.

Option 2: 36 × 10⁶ J

Incorrect choice. This distractor represents a common misunderstanding of the core principles of Work and Energy.

Option 3: 0.36 × 10⁵ J

Incorrect choice. This distractor represents a common misunderstanding of the core principles of Work and Energy.

💡 Study Guide: This question tests core syllabus concepts from Work and Energy. For formulas, key summaries, and mock exam reference guides, read the full Work and Energy Revision Notes.

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