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QPages 218-219: Q10: HC Verma: Concepts of Physics - Volume 2 Thermal and Chemical Effects of Electric Current Pages 218-219: Q10 Solution: An electric kettle used to prepare tea, takes 2 minutes to boil …

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often divide the energy in joules by 3600 instead of 3.6×10⁶, treating 1 kWh as 3600 J. Remember that 1 unit = 1000 W·h = 3.6 MJ, so to convert J to units divide by 3.6×10⁶. This keeps the cost calculation correct.

An electric kettle used to prepare tea, takes 2 minutes to boil 4 cups of water 1 cup contains 200 cc of water) if the room temperature is 25�C. a) If the cost of power consumption is Re 1.00 per unit 1 unit = 1000 watt-hour), calculate the cost of boiling 4 cups of water. b) What will be the corresponding cost if the room temperature drops to 5�C?

Step-by-Step Verified Solution

**Answer:** (a) 7 paise (b) 9 paise. **Step-by-Step Explanation:** (a) Q=0.8×4200×75=252000Q = 0.8 \times 4200 \times 75 = 252000 J. Units = 252000/(1000×3600)=0.07252000/(1000 \times 3600) = 0.07 = 7 paise. (b) Q=0.8×4200×95=319200Q = 0.8 \times 4200 \times 95 = 319200 J. Units = 319200/3.6×106=0.0886≈0.09319200/3.6 \times 10^6 = 0.0886 \approx 0.09 = 9 paise [citation:9].

All Questions in this Chapter

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