Transcript Chapter 22

Chapter 22 Summary
Electric Fields
E = F/q0
Electric Field Lines are merely to visualize patterns in electric
fields.
1- The direction of the tangent to the field lines at any point is the
direction of E at that point.
2- The number of lines per unit area is proportional to the
magnitude of E.
The electric field due to a point charge (q) at point which is a
distance r away:
E = k |q|/r2 point away from q if q is positive
E = k |q|/r2 point toward q if q is negative
If there are many charges q1, q2, q3, …, qn:
Use “superposition”: the net field is the vector sum of the fields due
to each of the n charges.
The electric field due to a dipole [p = q x d] (when z >> d) is:
Edipole = 2k p/z3, and is directed along the dipole axis.
The torque due to a dipole is:
= p x E
The potential energy due to a dipole is:
θ

U θ  U θr   τ dθ
θr
The work done by the field on the dipole is:
W = -DU = Ui – Uf
The applied work by an external agent is:
Wagent = Uf – Ui