10.1: Electric Charge and Electric Force

Describe the electric force that results from the interactions between charged objects or systems.

10.1.A.1 Charge is a fundamental property of all matter.

• 10.1.A.1.i Charge is described as positive or negative.

• 10.1.A.1.ii The magnitude of the charge of a single electron or proton is the fundamental unit of charge.

• 10.1.A.1.iii Charge is a scalar quantity.

• 10.1.A.1.iv Point charge is used to denote the model where the physical size of a charged object or system is negligible in the context of the situation being analyzed.

10.1.A.2 Coulomb’s law describes the electrostatic force between two charged objects as directly proportional to the magnitude of each of the charges, and inversely proportional to the square of the distance between the objects.

10.1.A.3 The direction of the electrostatic force depends on the signs of the charges on the interacting objects and is parallel or antiparallel to the line of separation between the objects.

• 10.1.A.3.i Two objects with charges of the same sign exert repulsive forces on each other.

• 10.1.A.3.ii Two objects with charges of the opposite sign exert attractive forces on each other.

10.1.A.4 Electric forces are responsible for some of the macroscopic properties of objects in everyday experiences. However, the large number of particle interactions that occur make it more convenient to treat everyday forces in terms of non-fundamental forces called contact forces, such as normal force, friction, and tension.