1 The Electric Field

2 A region in space around a charged object in which a stationary charged object experiences an electric force because of its charge. IT’S A FORCE FIELD!

Electric Field An electric field –is the space that surrounds any charged object. –is a vector quantity having magnitude and direction. –has a magnitude at any point that is the force per unit charge. –obeys the inverse-square law for a point source.

Electric Field Field lines –are used to visualize an electric field. –show the direction of an electric field - away from positive and toward negative. –show the intensity of an electric field: Lines bunched together  field is stronger Lines farther apart  field is weaker

5 Field Lines DO NOT REALLY EXIST! A useful method for representing the strength and direction of an electric field at a point in space.

6 Field Lines

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10 The Electric Field Electric Field strength is a ratio between the force on the charged particle and the charge of the particle

11 The Electric Field Q + qoqo E q o is a “test charge” (proton)

12 The Electric Field Q + qoqo E q o is a “test charge” (proton)

13 The Electric Field Electric Field strength depends on charge and distance. The closer that q o gets to Q, the stronger the force between them Oh yeah, field strength is a VECTOR quantity!

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The strength of an electric field is measured by the force A.exerted on a charge in the field. B.between electric field lines. C.between oppositely charged parallel plates. D.all of the above. 15

The direction of an electric field, by convention, is the direction of force that the field would exert on A.an electron. B.a proton. C.an atom. D.all of the above 16

Electric Potential Electric potential energy is the energy possessed by a charged particle or other object due to its location. If a particle is released, it accelerates away from the sphere, and its electric PE changes to KE.

Electric Potential Batteries and generators pull negative charges away from positive ones, doing work to overcome electrical attraction. The amount of work done depends on the number of charges and the separation distance. Work done by the battery and generator becomes available to a circuit as electric potential energy.

Electric Potential Electric potential energy per charge Energy that a source provides to each unit of charge charge electric potential energy Electric potential =

Electric Potential Electric potential and voltage are one and the same. The unit of measurement is the volt. 1 Coulomb 1 Joule 1 Volt =

Voltage Sources A potential difference exists when the ends of an electrical conductor are at different electric potentials. Batteries and generators are common voltage sources. Charges in a conductor tend to flow from the higher potential to the lower potential. The flow of charges persists until both ends reach the same potential. Without a potential difference, no flow of charge will occur.

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Electric potential energy (like all forms of energy) is measured in joules. Electric potential (electric potential energy per charge), on the other hand, is measured A.in volts. B.in watts. C.in amperes. D.also in joules. 24

When you do work on an electrically charged particle, you change the particle's A.charge. B.potential energy. C.capacitance. D.power. 25

When you increase the potential energy of a charged particle, you increase its ability to A.do work on something else B.charge other particles. C.conduct. D.transform to heat. 26

Electric potential, measured in volts, is a ratio of A.charge to the square of the separation distance. B.current to resistance. C.energy to charge. D.power to current. 27