Electrostatics

10,096 views
10,008 views

Published on

Describes electrostatic principles and concepts.
**More good stuff available at:
www.wsautter.com
and
http://www.youtube.com/results?search_query=wnsautter&aq=f

Published in: Education, Technology, Business
3 Comments
7 Likes
Statistics
Notes
  • good job
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • This is very helpful. Thank you!
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • ALSO
    I have written six books
    'Sticks - A Golfer’s Tale' - A hacker’s dream comes true.
    'Fish Farm' - Revenge of the old people.
    'Coach' - A mystery in Old school football town in a rural, bigoted, fifties town.
    'The Three Dollar Phoenix' - A mystery set in Newark, New Jersey in the 1970s.
    'The Divine Comedy MMIX' - A humorous play about Jesus returning.
    'The Blood of Judas' - A horror story of revenge set in Nazi Germany.
    All are available at www.smashwords.com
    I have video trailers for 'Coach', 'Fish Farm' and 'The Blood of Judas' at:
    http://www.youtube.com/watch?v=xXSD5Kz-fDY
    http://www.youtube.com/watch?v=a9PTRb14ldc
    http://www.youtube.com/watch?v=ToPp9k9Oq-o
    http://www.youtube.com/watch?v=3eBhMZbsP-I
    Please take a look. Thanks.
    Walt Sautter - wsautter@optonline.net
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Views
Total views
10,096
On SlideShare
0
From Embeds
0
Number of Embeds
723
Actions
Shares
0
Downloads
568
Comments
3
Likes
7
Embeds 0
No embeds

No notes for slide

Electrostatics

  1. 1. W. Sautter 2015
  2. 2. Electrostatics is the study of the effects of stationary charges on each other in their surroundings. Charges are created by the transfer of electrons to or from one body to another. (Protons are NEVER transferred.) Objects with equal numbers of protons and electrons are neutral. They have no net charge. Objects with more electrons than protons are charged negatively Objects with less electrons than protons are charged positively. 2
  3. 3. - + + + - + -- ++ - -Likes repel Likes repel Unlikes attract Unlikes attract 3
  4. 4. 6.25 x 10 18electrons 1 coulomb Charge on 1 electron = - 1.6 x 10 –19 coulombs Charge on 1 proton = + 1.6 x 10 –19 coulombs 4
  5. 5. Fg = gravity force between m1 and m2 separated by a distance r G is the Universal Gravitational Constant The weight of an object is its mass times g’, the gravity value at location r 5
  6. 6. Fe = electrostatic force Between m1 and m2 separated by a distance r k is Coulomb’s Constant Coulomb’s Law is an inverse square law similar to the Law of Gravitation It is dissimilar in that electrostatic forces can be attraction or repulsion. Gravity is attraction only. Electrostatic force is strong, gravity is very weak. 6
  7. 7. 7
  8. 8. Gravity is classified as a weak force because huge amounts of mass are required to create a reasonably large force. Note the very small value of the force constant. Electric forces is classified as a strong force because small charge quantities can to create large forces. Note the very large value of the force constant 8
  9. 9. 9
  10. 10. Electric charges are detected by the presence of an electric field (E). Recall that a gravity field can be detected by its influence (attractive force) on a mass (often called a test mass). Electric fields are detected by their influence (attractive or repulsive forces) on a charge (often called a test charge). Electrically charged bodies can be created by physically rubbing electrons off one object on to another. For example, rubbing a rubber rod with fur will transfer electrons from the fur to the rod which becomes negatively charged (it has extra electrons). Rubbing a glass rod with silk will transfer electrons from the rod to the silk. The rod is charged positively (it has missing electrons). 10
  11. 11. - - - - - - - - - Charged rod Leaves of electroscope Diverge (like charges repel) An Electroscope is an instrument used to measure the presence of an Electric field (presence of charged bodies). Moveable leaves 11
  12. 12. - - - -- - - - NEUTRAL OBJECT - - - -- - - - CHARGING BY CONDUCTION WHEN OBJECT IS TOUCHED BY THE CHARGED ROD ELECTRONS MOVE FROM THE ROD TO THE SPHERE UNTIL ELECTROSTATIC EQUILIBRIUM IS REACHED OBJECT IS NOW NEGATIVELY CHARGED - - - - - - 12
  13. 13. INDUCTIVE CHARGING CHARGED RUBBER ROD (EXCESS ELECTRONS) Electrons on sphere move to the opposite side due to repulsion of electrons on the charged rod 13
  14. 14. Electric Field E is always out of plus (+) into minus (-) Charged Plates 14
  15. 15. Recall that a gravity field (g) is measured by dividing the force acting on it (its weight(w) in Newtons ) by the mass quantity (m) in kilograms An electric field (E) is measured by dividing the force acting on it (in Newtons ) by the charge quantity (q) in coulombs (C ). g in N / Kg E in N / C 15
  16. 16. + - - - - + - - - - E E Scale Scale As Electric field strength increases, the Force on a test Charge increases. This is similar to the weight of a Mass increasing in a stronger Gravity field Test charge Test charge 16
  17. 17. Electric Field Charged Plates + Force E = Force (N) / Charge (Coul) 17
  18. 18. + Lines of Flux spread over a greater area as distance from charge increases and field strength weakensE = k q / r2 18
  19. 19. (1) E = F/q (by definition) (2) F = kq1 q2 / r2 (Coulomb’s Law) (3) E = kq1 q2 / r2 q2 ( by substitution) E = kq / r2 q = point charge in coulombs k = coulomb’s constant r= distance from charge in meters E = electric field strength at that point (N / C) 19
  20. 20. Electrical Potential is defined as the work required to move a charge over a distance in an electric field. Electrical potential is measured in volts. One volt equals one joule (work) divided by charge (coulombs) In a uniform electric field (a field between two parallel charged metal plates) , potential (V) equals work (W) divided by charge (q). Therefore, since work equal force times distance and force equals the electric field strength (N/C) times charge in coulombs (C) , potential equals electric field times distance the charge moves. V = W / q = (F x d) / q = (F / q) x d = E x d V (volts) = E ( N/C) x d (m) 20
  21. 21. 21 Click Here

×