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QPage 351: Q8: HC Verma: Concepts of Physics - Volume 2 Electric Current through Gases Page 351: Q8 Solution: Why does thermionic emission not take place in non-conductors?

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often assume heating any solid will cause thermionic emission, overlooking that insulators lack conduction‑band electrons and possess a work function far larger than the thermal energy $k_BT$, so no electrons are available to escape.

Why does thermionic emission not take place in non-conductors?

Step-by-Step Verified Solution

**Answer:** Non-conductors do not have free electrons and have a high work function. **Step-by-Step Explanation:** Thermionic emission requires free electrons that can escape the material when heated. Non-conductors (insulators) have electrons tightly bound to atoms and a very high work function, so they cannot emit thermions .

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