Triboelectric charging via electron transfer

Steps:

• Rubbing the rod with cloth causes friction, leading to electron transfer between them.
• The cloth becomes positively charged, indicating it has lost electrons.
• Electrons must have moved from the cloth to the rod to cause this loss.
• The rod gains electrons, resulting in a negative charge.

Why A is correct:

• Conservation of charge requires that if the cloth loses electrons (positive), the rod gains them (negative), as charge is transferred, not created.

Why the others are wrong:

• B: Electrons moving from rod to cloth would make the rod positive, not negative.
• C: Rod gaining electrons makes it negative, not positive.
• D: Protons are bound in nuclei and do not move during charging; only electrons transfer.

Final answer: A