Download
1 / 32
E N D
Chapter 22 Electric Fields In this chapter we will introduce the concept of an electric field. As long as charges are stationary, Coulomb’s law describes adequately the forces among charges. If the charges are not stationary we must use an alternative approach by introducing the electric field (symbol ). In connection with the electric field, the following topics will be covered: -Calculating the electric field generated by a point charge. -Using the principle of superposition to determine the electric field created by a collection of point charges as well as continuous charge distributions. -Once the electric field at a point P is known, calculating the electric force on any charge placed at P. -Defining the notion of an “electric dipole.” Determining the net force, the net torque, exerted on an electric dipole by a uniform electric field, as well as the dipole potential energy. (22-1)
Checkpoint 1: • The figure here shows a proton p and an electron e on an x-axis. What is the direction of the electric field due to the electron at • Point S and • Point R ? • What is the direction of the net electric filed at • c) Point R and • d) Point S?
q q (22-12)
Checkpoint 4: • The figure shows four orientations of an electric dipole in an external electric field. Rank the orientations according to : • The magnitude of the torque on the dipole • The potential energy of the dipole • Greatest first.
Checkpoint 3: • In the figure, what is the direction of the electrostatic force on the electron due to the external electric filed shown? • In which direction will the electron accelerate if its moving parallel to the y axis before it encounters the external filed? • If, instead, the electron is initially moving rightward, will its speed increase, decrease, or remain constant?
