Verified Solution • 2025–26 Session moderate

QPages 218-219: Q3: HC Verma: Concepts of Physics - Volume 2 Thermal and Chemical Effects of Electric Current Pages 218-219: Q3 Solution: The specification on a heater coil is 250 V, 500 W. Calculate…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often mistakenly assume resistance is directly proportional to power, leading them to double the resistance for the 1000 W coil. You must use the formula $R = V^2/P$ to recognize that at constant voltage, resistance is inversely proportional to power, meaning doubling the power halves the resistance.

The specification on a heater coil is 250 V, 500 W. Calculate the resistance of the coil. What will be the resistance of a coil of 1000 W to operate at the same voltage?

Step-by-Step Verified Solution

**Answer:** (a) R500=125 ΩR_{500} = 125\ \Omega (b) R1000=62.5 ΩR_{1000} = 62.5\ \Omega. **Step-by-Step Explanation:** P=V2/RP = V^2/R. (a) R=2502/500=125 ΩR = 250^2/500 = 125\ \Omega. (b) R=2502/1000=62.5 ΩR = 250^2/1000 = 62.5\ \Omega .

All Questions in this Chapter

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