18.5 Coulomb's Law

The magnitude F of the electrostatic force exerted by one point charge on another point charge is directly proportional to the magnitudes q 1 and q 2 of the charges and inversely proportional to the square of the distance r between them.

18.5 Coulomb's Law The magnitude F of the electrostatic force exerted by one point charge on another point charge is directly proportional to the magnitudes q 1 and q 2 of the charges and inversely proportional to the square of the distance r between them.

18.5 Coulomb's Law The proportionality constant k is known as Coulomb’s constant. It is given by, where ε 0 = 8.85  C 2 /N.m 2, is called the permittivity of free space.

A Model of the Hydrogen Atom

In the Bohr model of the hydrogen atom, the electron (-e) is in orbit about the nuclear proton (+e) at a radius of r = 5.29× m, as Figure shows. Determine the speed of the electron, assuming the orbit to be circular.

The Force on a Point Charge Due to Two or More Other Point Charges Consider the following three Charges on a Line. Find the net electrostatic force on q 3.

18.6 The Electric Field

The electric field is present in any region of space if there exists electric forces.

18.6 The Electric Field The electric field is present in any region of space if there exists electric forces. These electric forces can be detected using a test charge. Test charges are theoretical positive charges that do not alter the electric field to be detected.

18.6 The Electric Field The electric field is present in any region of space if there exists electric forces. These electric forces can be detected using a test charge. Test charges are theoretical positive charges that do not alter the electric field to be detected. Electric field at a point in space is defined as the force per unit test charge placed at that point.

The Electric Field of a Point Charge

Problem-29 Two charges are placed on the x axis. One charge (q 1 = +8.5  C) is at x 1 = +3.0 cm and the other (q 2 = -21  C) is at x 1 = +9.0 cm. Find the net electric field (magnitude and direction) at x = 0 cm.

Con-Ex:11Symmetry and the Electric Field Figure shows point charges fixed to the corners of a rectangle in two different ways. The charges all have the same magnitudes, but they have different signs. Consider the net electric field at the center C of the rectangle in each case. Which field is larger?

Con-Ex:11Symmetry and the Electric Field

The Parallel Plate Capacitor

Electric field between two parallel plates