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A polythene piece rubbed with wool is found to have a negative charge of 3.52×10⁻⁷ C. What is the number of electrons transferred?

Asked in GUJCET 2023 · Properties of charge

• (1) 1.1×10¹²
• (2) 2.2×10¹²
• (3) 4.4×10¹²
• (4) 5.5×10¹²

Step-by-step solution

Why the other options are wrong

• (1) Half the correct count - what you get by dividing by 2e=3.2×10⁻¹⁹ C instead of e. Each electron carries just e.
• (3) Twice the correct count; no single slip gives it. Sanity check: (3.52×10⁻⁷)/(1.6×10⁻¹⁹)=2.2×10¹².
• (4) No single slip gives 5.5×10¹². Sanity check: that many electrons would carry 5.5×10¹²×1.6×10⁻¹⁹=8.8×10⁻⁷ C, not 3.52×10⁻⁷ C.

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