Verified Solution • 2025–26 Session moderate

QPages 395-396: Q23: HC Verma: Concepts of Physics - Volume 2 X-Rays Pages 395-396: Q23 Solution: Heat at the rate of 200 W is produced in an X-ray tube…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students frequently insert $V=20$ (kV) directly into $P=VI$, forgetting to convert to volts; this yields a current three orders of magnitude too high. Always change $20\text{ kV}$ to $20\times10^3\text{ V}$ before applying $P=VI$.

Heat at the rate of 200 W is produced in an X-ray tube operating at 20 kV. Find the current in the circuit. Assume that only a small fraction of the kinetic energy of electrons is converted into X-rays.

Step-by-Step Verified Solution

**Answer:** Current = 10 mA. **Step-by-Step Explanation:** Given: Heat produced = 200 W, V=20V = 20 kV. Almost all kinetic energy of electrons is converted into heat (only a small fraction becomes X-rays).
P≈Vi⇒200=20×103×i⇒i=0.01 A=10 mAP \approx Vi \Rightarrow 200 = 20 \times 10^3 \times i \Rightarrow i = 0.01 \text{ A} = 10 \text{ mA}

All Questions in this Chapter

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