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## PowerPoint Slideshow about ' Electric Field' - yasir-molina

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### Electric Field

Analogy

The electric field is the space around an electrical charge

just like

a gravitational field is the space around a mass.

Electric Field

- Space around a charge.

Van de Graaff Generator

- Builds up static electric charges.

Electric Field Vector, E

- E = F/ qo
- qo , positive test charge
- E is a vector quantity
- Unit: N/C
- E is analogous to the gravitational field, g, where g=F/m

Example 1

- A charge of 3µC is used to test the electric field of a central charge of 6C that causes a force of 800N. What is the magnitude of the electric field?
- Answer: 2.7 x108 N/C

http://higheredbcs.wiley.com/legacy/college/halliday/0471320005/simulations6e/index.htm?newwindow=true

Electric Field Lines

- Lines that indicate the strength and direction of the electric field.
- The more dense the lines, the stronger the field.
- Electric field vectors are tangent to the curve.
- Simulation

http://online.cctt.org/physicslab/content/applets/pointcharges/elefi_z.htm

Conductors and Electric Fields (under electrostatic conditions)

- “The electric field is zero inside a charged conductor”.
- “Excess charge on an isolated conductor resides on the surface”.
- “Excess charge accumulates on sharp points”.
- Electric field lines meet the conductor perpendicular to the surface of the conductor.

Shielding

- The electric field is zero inside a charged conductor.

Where are you safe during a thunderstorm?

- In a car or
- Outdoors

Why can you not get radio reception in a tunnel or in a steel bridge?

Electric Field for a Point Charge

Using E=F/qo and Coulomb’s Law prove:

E = k Q

______

r2

where Q is the central charge.

Example 2

- A test charge of +3µC is located 5m to the east of a -4µC charge.
- A) Find the electric force felt by the test charge.
- B) Find the electric field at that location.
- Answer: 4.32x10-3 N, 1.44 x 103 N/C along the –x axis.

Example 3

- If a test charge is moved to a location three times as far as its original location, how does the electric field change?

Example 4

- Calculate the electric field felt by a test charge located half way between a charge of +1C and a charge of -3C, that are 2m apart.
- Answer: 1.8 x 1010 N/C

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