Chapter 21 Electric Charge In a this chapter we will new property of matter introduce that is known as electric change sg bol g we will describe the Moreover following properties of charge Types of electric charge o g two charges Forces law Coulomb s a Charge quantization conservation Charge if uber that it was known since is E piirically ancient fines on cloth it acquires the rubbed property of attracting light objects such as feathers This phenomena was attributed to a new called property of matter felechnicchargetf Experiments show that are electric distinct types of two charges there Positive color code Negative color code blue black red Expericents showed on charged objects that ot ch positive or 1 m thes negative repel each other 1 12 Charges of opposite type attract each other we on as an unknown charge follows silk cloth and charge rod is can To figure out the recipe is We charge a glass rod by rubbing it know that with the glass rod is positive the The suspended in such a way keep its charge and also so it is able the force applied by charge with the unknown We with the Two out co sigh new unknown charge to rotate freely under the suspended glass rod approach are es possible 1 The two objects repel each other We then conclude unknown charge is that the positive L H l 2 The two objects attract each other then we unknown charge conclude is that the negative kind that of cess ed see charges are fluid In Benjamin Franklin s day it related was to However experiments done by Ernest Rutherford the revealed the structure 19th century alter of atom the at the beginning of and in particular of have has sizes of a size Atous consist of telectrons nucleus Ato s Nucleus The nucleus consists of of particles proton ed the 5 1010m 5 10 is two types positively charged neutron neutral not charged The do also includes the electron negatively charged 1 We use the the electron ed proton charge ad call e elementary change e ed te for sy bol the 2 Ato s are electrically neutral as atonic unber The u ber of electro s is equal to the the uber of protons sybol Z This is known The chemical properties are determined by 7 the and as sun ofthe cuber of protons the uber of neutrons is known sy bol A the A 235 u berof mass number protons neutron Notation 23 92 U 3 7 92 ueber of protons lelectrons Conservation of Charge e an on the If we rub the glass sild cloth we on charge is actually Aero a glass rod and a piece of silk see positive the same At the rod equal amount of negative charge that the silk cloth so Consider both unchanged rod with the charge appear ti appears net That suggests that rubbing does not create charges but only transfers charges fro Summarize In any process the change at the beginning equals the charge at the end of one body to the other the process chanteuse Conductors ed Insulators conductors are materials charges to move that allow freely Imperator Insulator Ex ples copper silver alumina mercury are materials that allow charges to move without resistance are materials through which charges cannot move freely Exeples are plastic rubber glass inductor by induction can changing an A conductor induction We then approach the negatively on an the rod insulator The conductor is be charged using iniatiall conductor with a charged charged rod The negative charges are fixed because plastic is h move the electrons of the These charges repel conductor whid freely ed they can at the other side of the copper end up The end of the copper rod that rod to the plastic rod thus gets is positively charged Noo opposite charges attract each other and an attractive force between the two rod ends there is closest Su cavite the induced charge has the opposite sign Coulomb s law a r q that distance two charges ad 92 placed Consider at The two changes exert a force on ead other to The force acts along the line connecting 2 The force is attractive for charges the charges the following characteristics has of for the opposite signand it the save sign is repulsive S 3 The magnitude of the force known could force is given by the as the equation F latif The constant permitivity so vacuum is known a constant