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Electric Fields

Electric Fields. What You Will Learn. An electric field is like a . An electric field is a . An electric field provides the that a will move if placed in the field. An electric field is composed of a series of imaginary. What you already know. Coulomb’s Law:. +. F.

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Electric Fields

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  1. Electric Fields

  2. What You Will Learn • An electric field is like a . • An electric field is a . • An electric field provides the that a will move if placed in the field. • An electric field is composed of a series of imaginary .

  3. What you already know • Coulomb’s Law: + F Note: is much smaller than !

  4. Electric Field • The electric field is the that a experiences divided by itself. • Note: The electric field is a and therefore has magnitude and direction. + F

  5. What is the • It is enough that it does not affect the field due to other charged objects. • It will move towards or away from other charged objects depending on whether it is charged similarly or dissimilarly from other objects.

  6. + + _ _ + + _ _ _ + + + _ _ _ + + + _ _ + _ _ + _ + + _ _ + + _ + _ + The Test Charge (Cont.) _ _ Test Charge moves from a positively charged object Test Charge moves a negatively charged object Negatively Charged Object Positively Charged Object

  7. Example A positive charge of 4.0 x 10-5 C experiences a force of 0.36 N when located at a certain point. What is the electric field intensity at that point? Note: The says nothing about the magnitude of charge , which is the of the that produces the that charge experiences.

  8. + + _ _ + + _ _ _ + + + _ _ _ + + + _ _ + _ _ + _ + + _ _ + + _ + _ + Electric Field Lines • Electric field lines, or of , provide a of the at any point in space from a charge. • Electric field lines show the that a would take if placed in the field. _ _

  9. Electric Field Lines • Electric field lines at and are always directed away from them towards . • Electric field lines do or except at the of or charges. • Electric field lines are () to the where they or . • Electric field lines . • The strength of the field is proportional to the magnitude of the charge and is directly related to the of field lines • the there are and the together they are, the the field.

  10. + + + + + + + + + + + + + + + + + + Electric Field Lines Due to a Point Charge Direction of field is . Density of lines is . Lines intersect .

  11. _ _ + + _ _ + + _ _ _ + + + _ _ _ + + + _ _ + _ _ + _ + + _ _ + + _ + _ + Note: An electric dipole consists of in and in . Electric Dipole Note: Force on a () is the field lines, and is the of the forces due to of the dipole acting on it.

  12. Examples from the Web http://www.cco.caltech.edu/~phys1/java/phys1/EField/EField.html http://phet.colorado.edu/sims/charges-and-fields/charges-and-fields_en.html

  13. + + + + + + + + + + + + + + + + + + Electric Fields and Conductors E • At equilibrium, excess charges will reside on the of a conductor. • The electric field is at any point within a conducting material at . • Charge within a conductor is from external electric fields because they or on the where excess charges reside. E-Field inside conductor

  14. Parallel Plate Capacitor • The parallel plate capacitor is an device used in all kinds of electronics. • Field lines in a parallel plate capacitor are and to one another, indicating a electric field. - - - - - - - - + + + + + + + +

  15. + + + + + + + + + + + + + + + + + + Electrostatic Force and Distance • For point charges: • The strength of the field as the distance .

  16. Electrostatic Force and Distance • For parallel plates: • The strength of the field is from one plate to the other. • Since , the will be .

  17. Force Force Distance Distance E-Field Intensity E-Field Intensity Distance Distance Force and Electric Field Strength vs. Distance Point ChargeParallel Plate

  18. Example (Millikan Oil Drop Exp.) An oil drop is negatively charged and weighs 8.5 x 10-14 N. The drop is suspended in an electric field intensity of 5.3 x 101 N/C. What is the charge on the drop? How many electrons is that?

  19. Key Ideas • Electric fields exists around any conductor or insulator that contains a charge. • The electric field intensity is a measure of the force on a test charge placed in the field. • The strength of the field is proportional to the density of field lines. • Field lines are perpendicular to all charged surfaces. • The electric field is always directed away from positive charges and towards negative charges.

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