Transcript Electric Fields 17-3

The Electric Field
Chapter 17-3
Pages 643-652
Electric Field Strength (p. 643-647)
- Electric force is a Field Force - capable of
acting through space (no physical contact
needed)
I’m not
touching
you!
I’m not
touching
you either.
Michael Faraday (1791-1867)
• He had a definition of
an electric field
• Electric Field - An area
in space around a
charged particle
• If another charged
particle enters this area
then electric forces are
felt.
Electric Field Lines p.648-652
• Lines that represent
magnitude and
direction of the
electric field.
• A visualization
technique
• The lines don’t
actually exist
Electric Field Lines p.648-652
• Good for analyzing field strength and
direction at certain points
• # of field lines is related to field strength
• → Stronger field = more lines
• The closer lines are together, the
stronger the field
Rules for drawing electric field lines
(pages 648-649)
1. Always start on the positive charge or infinity.
Always end on the negative charge or infinity
2. Number of field lines is proportional to the
magnitude of the charge
3. No two field lines can cross each other
Van de Graff generator
How does it work → basic mechanism
• A device that is used to
generate electric charge
1. A metal dome, a pulley
and belt, and a grounded
source of electricity
Van de Graff generator
How does it work → basic mechanism
2. The pulley moves
the belt past a
positively charged
comb at the
bottom of the
machine and
electrons from the
belt are pulled
onto the comb.
Van de Graff generator
How does it work → basic mechanism
3. The now positively
charged belt, moves up
to the top of the
machine (the dome)
and attracts electrons
to the positively
charged belt from the
dome and back down
to the bottom.
Van de Graff Parts
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1. Dome
2. Upper comb
3. Upper pulley
4. Positively charged belt
5. Negatively charged belt
6. Lower pulley
7. Lower comb
8. Discharge wand
9. Electric discharge
Van de Graff generator
How does it work → basic mechanism
4. The dome becomes more and more
positively charged as more and more
electrons are stripped off the dome and are
carried to the bottom.
• Anything touching the
dome will also have
electrons stripped away.