Electric Fields ch Electric Fields ch 2626Electric fields of point sources AND Electric fields of point sources AND E fields of other “common shapes”E fields of other “common shapes”

Electric FieldsElectric Fields

Electric fields of shapes include…..Electric fields of shapes include….. Point sourcePoint source Really long wireReally long wire Really wide flat planeReally wide flat plane Really spherical sphereReally spherical sphere

We’ve already discussed the point source and We’ve already discussed the point source and that electric Field lines point in the direction that electric Field lines point in the direction of the Force acting on a positive test charge.of the Force acting on a positive test charge.

Electric FieldsElectric Fields

For electric fields of multiple point charges, find For electric fields of multiple point charges, find the electric field from each point separately and the electric field from each point separately and then add them up (add as vectors with then add them up (add as vectors with direction)direction)

Electric Field Lines help visualize the e-field. Electric Field Lines help visualize the e-field. E field lines are closer where the field is strongerE field lines are closer where the field is stronger E field lines begin on a positive charge and end on a E field lines begin on a positive charge and end on a

negative charge.negative charge.

Electric Field of a Electric Field of a continuous charge continuous charge distributiondistribution

To find the e-field of other shapes, break the To find the e-field of other shapes, break the shape up into little bitsy tiny small pieces, each shape up into little bitsy tiny small pieces, each of which creates an electric field like a point of which creates an electric field like a point source. By summing these up (integrating) you source. By summing these up (integrating) you determine the e-field of the whole shape.determine the e-field of the whole shape.

Our book goes through the integration for a Our book goes through the integration for a long charged wire and a ring, plane and long charged wire and a ring, plane and sphere.(recommend reading these derivations)sphere.(recommend reading these derivations)

We’ll also look at one of the simulations on We’ll also look at one of the simulations on archive.org to see how these derivations are archive.org to see how these derivations are done. done.

Electric Field: affect on a Electric Field: affect on a charge in an e-fieldcharge in an e-field

A charged object in the e-field experiences a A charged object in the e-field experiences a force. force.

Using E = F/q determine the Force acting on Using E = F/q determine the Force acting on the charged object (where q is the charge on the charged object (where q is the charge on the object affected by the electric field E)the object affected by the electric field E)

Knowing F, you can determine the objects Knowing F, you can determine the objects motion using Newton’s 2motion using Newton’s 2ndnd law……F = ma law……F = ma