Electrostatics

Structure of the Atom All matter is made of atoms

Protons, neutrons & electronsThe protons are held tight in the nucleusThe electrons move around outside the

nucleusNormally, atoms have the same number of

protons & electronsThe protons & electrons cancel each other out

and there is no net charge, or neutral.

Static Electric Charge

• The result of transfer of electrons.• The electrons in the atoms can be removed or

added.• Lose electrons – positive net charge• Gain electrons – negative net charge

Electric Charge-Force Law

• Opposites attract. • Likes repel.

• Electrostatics

Ways to Charge an Object

• Friction:– When two objects come in contact, one object

may lose electrons– The other object will gain them!– How easily an object gains or loses electrons

depends on what it is made of!

Charge by Polarization

• Separation of charge in an object• The overall net charge of the

object is still neutral

Polarization!

Ways to Charge an Object

• Conduction– Electrons can be transferred from one object to

another by touching.– When a charged object touches another object,

some charge will transfer.– If the charged object is negative, some of the

electrons will leave the negatively charged object to the neutral object – leaving both objects with a negative charge!• They repel each other!!!!

Charge by Induction

• Objects can be charged by bringing a charged object near a neutral object

• The charged object will attract unlike charges in the neutral object and repel like charges

• Remember only electrons can move around!!!• If the neutral object is grounded, the repelled

charges will leave the object (go into the ground!)

• This leaves the once neutral object with a net charge

Charge by Induction

Charge by Induction

Electric Force

• Direction of electric forces between charged objects are given by the charge-force law

• The magnitude of the force depends on size of charge and distance!