Unit A: Electrostatics AP Physics C Review Unit A: Electrostatics

Electric forces and charges The electric force is one of four fundamental forces. The electric force is the result of electric charges. There are two kinds of electric charges. Electric charge is conserved. Electric charge is quantized. The charge on an electron is -1.60 x 10-19 C.

Methods of Charging an Object Conductors and insulators can be charged by contact. Conductors can be charged by induction. A charge can induce a surface charge in insulators by polarization. Charging by Induction Demonstrate this method of charging. ©2008 by W.H. Freeman and Company

Clarification: The conductor never touches the charged plate. © 2009 Richard White, LearnAPphysics.com

Coulomb’s Law kC = 8.99 x 109 Nm2/C2 Coulomb’s constant is sometimes written The electric force one charge exerts on another is given by Coulomb’s Law A negative force means attraction, positive means repulsion.

Superposition Superposition- the force on a charge due to several other charges is the vector sum of the forces from the other charges. ©2008 by W.H. Freeman and Company

© 2009 Richard White, LearnAPPhysics.com

Electric Field The presence of charges causes electric fields. The electric field at a location is the force / Coulomb of charge felt by a positive test charge at that location. The electric field caused by a point charge is Electric fields are measure in Newtons/Coulomb (or Volts/meter). The principle of superposition applies to fields as well.

© 2009 Richard White, LearnAPphysics.com

Electric Field of a Dipole An electric dipole consists of two equal and opposite charges that are a small distance apart. Far away from the dipole, the E field is ©2008 by W.H. Freeman and Company

Electric Field Lines Electric fields can be represented using electric field lines. Lines begin on positive charges (or infinity) and end at negative charges (or infinity). Lines enter or leave an isolated charge symmetrically. The magnitude of the field is shown by the number of lines in a given area. The number of lines entering or leaving a charge is proportional to the magnitude of the charge. At a large distance, every arrangement of charges approximates a point charge. Lines do not cross. ©2008 by W.H. Freeman and Company

© 2009 Richard White, LearnAPphysics.com

© 2009 Richard White, LearnAPphysics.com

©2008 by W.H. Freeman and Company