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When 10¹⁹ electrons are removed from a neutral metal plate through some process, the charge on it becomes _____.

Asked in GUJCET 2015 · Properties of charge

• (1) +1.6 C
• (2) -1.6 C
• (3) 10¹⁹ C
• (4) 10⁻¹⁹ C

Step-by-step solution

Why the other options are wrong

• (2) Wrong sign. Removing electrons leaves the plate short of negative charge, so it becomes positive; -1.6 C is what adding 10¹⁹ electrons would give.
• (3) Treats each electron as carrying 1 C. Each carries only e=1.6×10⁻¹⁹ C, so the number must be multiplied by e.
• (4) No single slip gives 10⁻¹⁹ C; that is roughly the charge of one electron, not of 10¹⁹ of them. Sanity check: q=ne=10¹⁹×1.6×10⁻¹⁹=1.6 C.

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