THE ELECTROSTATICS

THE NATURE OF ELECTRIC CHARGES

• Greeks used to rub amber on wool or fur to get it charged
• The piece amber would pick up non metal objects because it is temporarily charged
• It has this attractive property for some time so the effect is static
• If you bring a rubbed ebonite closed to a silver pith
• suspended by a thread the rod will attract the ball pith ball for some time

ELECTRIC CHARGES

• Chemical experiments proved that there are ions in a solution
• Confirmed the existence of positive and negative ions.
• Substances like the silver pith ball and the amber rod
• become oppositely charged
• Carrier of of electric charge is electrons and carrier of positive are protons

15.2 THE DETECTION AND MEASUREMENT OF ELECTRIC CHARGES

• The part of the rod that was in contact with the cloth is charged
• Rubber, plastic and glass are insulators
• Metals and your body are conductor thus metal in hand can't be charged statically
• The silver pith balls which are statically charged can be used to detect presence and sign of electric charges
• Electroscopes can define the qualitative measurement of an electric charge.

COULOMB'S LAW

• Charge that are alike repel and charges that are opposite attract each other
• Electrostatic force is similar to gravity
• Coulomb's law is the force between two charges separated by distance, experienced mutual force connecting the two charges
• Coulomb' s law mathematically F=kq1q2/r^2 in which K=9*10^9, vector equation
• Net force on one charge is equal to vector sum of all other electrostatic forces called superposition

15.4 THE ELECTRICAL FIELD

• Charges set up an electric field, E, is the measure of the force per unit charge experienced on
• At a particular location , Units of an electric field (N/M or N/C)
• Two point charges + Q and +q! brought near! test charge +q will be repelled along a radial vector out from + Q charge
• The electrical field between the two charges will vary depending on the location of the test charge
• Test charges taken always to be positive. Equation E= F/q, electrical field varies so it can also be written as KQ/r^2