Mechanism of Charging of an Object - Charging by Conduction

The process of transferring electric charge from a charged object to a neutral (or oppositely charged) conductor through direct physical contact, until electrostatic equilibrium is reached.

Key idea: Electrons flow from the region of higher electron concentration to lower, until both bodies reach the same electric potential.

Charging by conduction happens in four sequential steps:

1. Contact established: A charged body touches a neutral conductor.

2. Electron migration begins: Electrons move freely through the conductor's surface due to weak binding.

• If the charged body is negative, it pushes excess electrons onto the neutral conductor.
• If the charged body is positive, it pulls electrons away from the neutral conductor.

3. Equilibrium reached — Charge distributes until both bodies attain the same potential.

4. Bodies separated — The neutral conductor retains a net charge of the same sign as the charging body (but usually smaller in magnitude).

Real-Life Analogy

Think of two water tanks connected by a pipe at different water levels. Water (electrons) flows from the tank with a higher level (more electrons) to the one with a lower level, until both reach the same height (equal potential). Once disconnected, both tanks retain their new water levels — similar to how conductors retain charge after separation.

Example 1: Negatively Charged Rod

A negatively charged ebonite rod touches a neutral metal sphere.

• Electrons flow from rod to sphere.
• Sphere becomes negatively charged.
• Rod's negative charge decreases slightly.

Example 2: Positively Charged Rod

A positively charged glass rod touches a neutral conductor.

• Electrons flow from conductor to rod.
• Conductor becomes positively charged (electron deficient).
• Rod's positive charge decreases slightly.

• Conduction requires direct contact; induction does not.
• The neutral body acquires the same sign of charge as the charging body.
• Charge is shared, not duplicated — total charge before and after contact is conserved.
• For identical spheres, final charge splits equally; for unequal spheres, distribution depends on size/capacitance.
• Grounding (earthing) can neutralize the object by providing/removing electrons via the earth.