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A charged glass rod is brought close to two touching neutral metal spheres but does not touch them. The spheres are then separated while the rod is still nearby. What method of charging has just been used on the spheres?
ACharging by conduction
BCharging by friction
CCharging by a dielectric
DCharging by induction
Answer & Solution
Correct answer: D. Charging by induction
1. Charging by induction creates an unbalanced charge on a second object just by bringing a charged object near it, without contact.
2. Here the glass rod approaches without touching the spheres, which matches this description exactly.
3. Charging by conduction instead requires direct contact between the objects, which did not happen here, so it is ruled out.
4. The trap is assuming any nearby charged object must touch something to charge it; induction works purely through the nearby field.
_Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section Transfer and Separation of Charge_
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