Static electricity is the result of an imbalance of electric charges on a surface, typically caused by the following mechanisms:

1. Triboelectric Effect (Friction-Induced Charging)
When two different materials rub against or separate from each other, electrons transfer from one surface to the other, creating a charge imbalance.

Example: Rubbing a plastic comb through dry hair transfers electrons from the hair to the comb, making the comb negatively charged and the hair positively charged.

Common Scenarios:
Clothing (polyester) rubbing against the body.
Conveyor belts interacting with packaging materials.
Workers walking on insulative flooring.

2. Contact-Induced Charge Separation
Even without significant friction, separating two materials after contact can cause charge transfer.

Example: A person touching a metal doorknob after walking across a carpet may experience a shock as accumulated static charge discharges through the knob.

3. Electrostatic Induction
A charged object near a conductor causes a redistribution of charges within the conductor, creating an induced charge.

Example: A charged plastic rod brought near a metal sphere causes electrons in the sphere to migrate, creating a polarized charge distribution.