Energy consumed in a home is 250 units then the total energy in Joule will be:

Question

Energy consumed in a home is 250 units then the total energy in Joule will be:

1. A. 9 × 10⁵
2. B. 8 × 10⁶
3. C. 9 × 10⁸ (Correct answer)
4. D. 10⁵

Correct Answer

Option C — 9 × 10⁸

Detailed Solution & Explanation

The correct answer is 9 × 10⁸.

Key Points

• In electricity billing, one 'unit' means one kilowatt-hour (1 kWh), which is the commercial unit of electrical energy, as distinct from the joule, the SI unit.
• The conversion is derived as follows:
• 1 kWh = 1000 watts × 3600 seconds = 3.6 × 10⁶ joules.
• Therefore the total energy for 250 units is:
• 250 × 3.6 × 10⁶ = 900 × 10⁶ = 9 × 10⁸ joules, which is option (C).
• Remember the underlying definitions: 1 watt = 1 joule per second, and energy = power × time.
• A kilowatt-hour is simply the energy consumed by a 1 kW appliance running for one hour.

Exam Tip

• commit 1 kWh = 3.6 × 10⁶ J to memory — it appears repeatedly in state PSC physics questions.
• Candidates who wrongly use 1 kWh = 1000 J will land on the distractor 10⁵, which is precisely why that option is offered.

प्रश्न (हिन्दी में)

किसी घर में एक महिने में ऊर्जा की खपत 250 यूनिट होती है तो कुल ऊर्जा जूल में होगी:

1. A. 9 × 10⁵
2. B. 8 × 10⁶
3. C. 9 × 10⁸
4. D. 10⁵