Mechanism of Charging of an Object - Charging by Induction

The process of charging a neutral conductor without any direct contact with a charged object, by redistributing charges within the conductor through electrostatic influence.

Case A: Bringing a positively charged rod near a neutral metal sphere

Result: Conductor becomes negatively charged — opposite in sign to the inducing rod.

Case B: Negatively charged rod → by symmetry, the conductor ends up positively charged.

Critical Rule: The earth connection must be removed before the charged object is taken away. If removed after, all induced charge escapes to earth and the conductor remains neutral.

For a dielectric medium with dielectric constant K, placed near a charge q, the induced charge q_i​ is given by:

\[q_i=-q\left(1-\frac{1}{K}\right)\]

Where:

• q = inducing charge
• K = dielectric constant of the material
• q_i​ = induced (bound) charge on the dielectric surface

• Analogy: Think of a crowded room (conductor) where a celebrity (charged rod) enters. People near the celebrity (electrons) rush toward them, leaving the far side of the room emptier — without anyone actually leaving through the door (no charge transfer), until an exit (grounding) allows some people to leave permanently.
• Real-life application: Lightning rods and van de Graaff generator demonstrations use induction principles; static charge buildup near charged screens/balloons attracting neutral paper bits is a classic induction demonstration.

• Induction charges a conductor without contact, via internal charge redistribution.
• The conductor always acquires a charge opposite in sign to the inducing charge.
• Order of operations matters: ground → disconnect earth → remove charged object.
• Charging by induction is permanent only if grounding is done correctly.
• Distinguish clearly from conduction (contact, same-sign charge) and friction (rubbing, opposite charges on two bodies).