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

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 generator How does it work → basic mechanism

Van de Graff Parts

• 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.