1. Stream lines

2. front plate slightly charged induces opposite charge on back plate. Brushes pull off charges charges collected in leyden jar (capacitor)

3. Electric Field

4. Definition Electric field is the strength & direction of the forces in space surrounding a positive test charge

5. Electric field as coulomb’s law F = q 1 * (k q 2 /d 2 ) rewrite the force equation F = q 1 * E q 1 is the positive test charge E is the field created by charge(s) q 2

6. Top tips on electric field E=0 inside a metal (faraday) cage Field lines go from + to – charges Closer field lines are stronger

7. Electric Field between 2 unlike charges + - A B C Note that the distance between electric field lines at C is shorter than that at B. Distance between electric field lines at B is shorter than at A.

8. Electric Field between 2 charged plates positive negative

9. Electric Field between 2 charged plates ++++ ++++ ---- ----

10. coulombs, joules, volts Coulomb= unit of charge Joule = unit of energy Volt= unit of energy per charge

11. coulomb How many charges are in 1C? coulomb? 1C is about 6 billion billion charges) (1/1.6 x 10 -19 = 6.25 x 10 18 ) The man, the law Charles Coulomb~1750

12. Joulesof energy Charges have a type of energy called electron potential energy (PE e or U) High energy: + is close to +: ++ or + is far from –: + -

13. It takes work to move charges against (opposite) an electric field High energy work needed to move + charge (W = F*d) E F + low energy

14. POSITIVE charge moving in an E field. (a) When a positive charge moves in the direction of an electric field, the field does positive work and the potential energy decreases. Work = q o E d

15. Volts is an energy density Voltage is also called potential 1 volt = 1 joule / 1 coulomb Example: 12 V battery: every coulomb of charge has 12 joules of energy

16. Examples Static balloon 9 V battery (1hr,1A) 1 joule of energy 9x10 4 joule energy 0.001 C of charge 1x10 4 C of charge 1/.0001 = 1000 volts 9/1 = 9 Volts

17. Another c,j,v example Van de graaf static generator has.. 1,000,00 volts (high) 1 joule of energy (low).00001 coulombs of charge 1,000,000 v = 1 j/.00001c

18. Uniform electric field2 situationsPoint Charges Force:F=q*EForce= k q 1 *q 2 / d 2Electric potential energy PE= F*d = q*E*dPE = F*d = k q 1 *q 2 / d Voltage (electric potential) V= PE/q 1 = q*E*d /q = E*d V= PE/q 1 = k q 2 / d 2 Voltage difference:  Ve =  PE/q 1 = E*  d  Ve =  PE/q 1 = k q 2 / d 2 - kq 2 / d 1

19. It takes work to move + charge against static forces like it takes work to lift against gravity PE final +++++ + Pe iniitial work = gain in PE = F*d

20. Electrostaticsgravitational Force: F= kq 1 q 2 / d 2 F= Gm 1 m 2 /d 2 Field E= F/q 1 = kq 2 /d 2 g = F/m 1 = Gm 1 /d 2 potential energy PE= F*d = kq 1 q 2 / dPE = F*d= Gm 1 m 2 /d (using field) =qE*d = mg*h Potential V= PE/q 1 = kq 2 / dU= PE/m 1 = G m 2 / d (Using field) = E*d = g*h