Static Electricity

Electric Charge General Properties –Electrons carry negative charge and exist outside of the nucleus –Protons carry positive charge and exist inside the nucleus –In solids, electric charge is carried by the smaller electrons because they move easier –In liquids and gases the charge can be carried by electrons or protons

Electric Charge An electron carries the smallest amount of charge that can exist –Protons have a charge that is the same size as an electron but has the opposite sign (positive) When working with charges, opposite charges attract while like charges repel each other (push away) just like magnets –This pushing and pulling because of charge is called the electrostatic force

Types of Materials Conductors –Materials that contain a lot of free electrons –Electrical charge can move easily through these materials Most metals are good conductors (copper is used in wiring) Insulators –Materials that do not have many free electrons –The charge in or on an insulator will remain stationary Things like plastics and glass are good insulators

Charged Objects When an object has an unequal number of protons and electrons the object is said to be ‘charged’. –If there are more electrons it will have a negative charge –If there are more protons it will have a positive charge –In solids only the electrons move, the number of protons doesn’t change

Charge by Contact If you have an object with a charge and you touch it to a neutral object, a portion of the charge will be transferred to the neutral object. –Afterwards both objects will be charged the same

Charging by Friction Charging by friction –When two objects are rubbed together, friction between the two objects will transfer electrons from one object to another –Whether an object will gain or lose electrons during friction can be determined by looking at the triboelectric series The object that is lower on the list will gain electrons

Charging by Induction a charged object is brought near but not touched to a neutral conducting object The presence of a charged object near a neutral conductor will force (or induce) electrons within the conductor to move The movement of electrons leaves an unbalance of charge on opposite sides of the neutral conductor While overall the object is neutral (i.e., has the same number of electrons as protons), there is an excess of positive charge on one side of the object and an excess of negative charge on the opposite side of the object

Charging by Induction Once the charge has been separated within the object, a "ground" is brought near and touched to one of the sides. The touching of the ground to the object permits a flow of electrons between the object and the ground The flow of electrons results in a permanent charge being left upon the object When an object is charged by induction, the charge received by the object is opposite the charge of the object which was used to charge it.

Electroscope