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QPage 351: Q6: HC Verma: Concepts of Physics - Volume 2 Electric Current through Gases Page 351: Q6 Solution: An isolated metal sphere is heated to a high temperature. Will…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often assume the sphere stays neutral because it started uncharged, overlooking that in an isolated conductor the emitted electrons have nowhere to return; once thermionic emission occurs the sphere loses negative charge and therefore acquires a net positive charge.

An isolated metal sphere is heated to a high temperature. Will it become positively charged due to thermionic emission?

Step-by-Step Verified Solution

**Answer:** Yes, it will become positively charged. **Step-by-Step Explanation:** When the isolated metal sphere is heated, some free electrons gain enough thermal energy to overcome the work function and escape from the surface (thermionic emission). Since electrons (negative charge) leave the sphere, the sphere is left with a net positive charge .

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