A comb attracts small pieces of paper due to

Electrostatic force is the force between electrically charged objects, given by Coulomb's law. When one object develops a net electric charge (through processes like friction) and is brought near a neutral object, it induces a redistribution of charge on the neutral object's surface, and the resulting Coulomb attraction can pull the neutral object toward it.

Rubbing a comb against dry hair transfers electrons between the two surfaces, leaving the comb with a net electric charge. When this charged comb is brought close to small, light pieces of paper, it induces an opposite charge on the near surface of each paper piece. Because the induced opposite charge sits closer to the comb than the like charge on the far side, the net electrostatic force between the comb and the paper is attractive, and the light paper pieces are pulled toward the comb.

• Frictional force: rubbing is the mechanism that charges the comb, but once the comb is charged, the force pulling the paper across the gap is not friction itself, since the comb and paper are not in sliding contact.

• Magnetic force: this would require a magnetic field acting on a moving charge or on a material with an appreciable magnetic dipole moment, such as iron or nickel. An ordinary rubbed comb produces no appreciable magnetic field, and paper's own magnetic response is negligible at this scale, so this interaction cannot explain the observed attraction.

• Gravitational force: it depends on the product of the two masses and falls off with distance; for objects as light as a comb and small paper scraps, this force is many orders of magnitude too small to produce any visible attraction.

The attraction observed here is therefore governed by electrostatic force, arising from charge induction between the charged comb and the neutral paper.