Static Electricity

All objects contain electrical charges. These charges come from three subatomic particles: ProtonsElectronsNeutrons

Characteristics of subatomic particles: Particle Charge MassLocation Proton positive 1 amu nucleus Electron negative.0005 orbits Neutron neutral 1 amu nucleus

Charles Coulomb standardized the unit of electric charge which bears his name. 1 Coulomb is the charge on 6.24 x electrons. The charge on 1 electron is 1.60 x Coulombs.

Static Electricity Charge is measured in Coulombs. Proton x C Electron x C Mass is measured in kilograms. Proton1.673 x kg Electron9.109 x kg Neutron1.675 x kg

Objects containing more of one type of charge than another are electrically charged. Static Electricity Positively charged objects have more protons than electrons (a deficiency of electrons). Remove electrons - positive charge Add electrons - negative charge

Static Electricity First Law of Electrostatics: Unlike Charges Attract Each Other Like Charges Repel Each Other Electroscopes are used to demonstrate the separation of charges.

The Law of Conservation of Charge Charge can neither be created or destroyed. It can only be transferred. Static Electricity

Conductors: Permit the flow of electric charge from one atom to the next. The charges that flow are electrons. Static Electricity

Conductors: Most metals are good conductors. Electrons in the outer quantum levels are free to “roam” from atom to atom. Static Electricity

Insulators: Prevent or restrict the flow of electrical charge. Insulators can be hold a charge, but only a small area remains charged. Static Electricity

Insulators: Glass, dry wood, plastic, cloth, and dry air make good insulators. Electrons are bound to specific atoms in shared covalent bonds. Static Electricity

Separation of charge: Friction between two insulators causes heat that separates electrons from their atoms. Static Electricity

Charging by conduction: Charge can be transferred when two objects are brought in contact with each other. When the object touch, there is a transfer of charge and the objects have the same charge. Static Electricity

Charging by induction: Charge can be induced when two objects are brought near each other. Grounding the object induces the opposite charge. Static Electricity

Electric forces: - exerted at a distance - directly proportional to charge - inversely proportional to distance Static Electricity Coulomb’s Law k = 8.99 x 10 9 Nm 2 / C 2 k = 8.99 x 10 9 Nm 2 / C 2

A gravitational field exists in the area of space generated the Earth’s mass. It is not tangible, but it has a tangible effect on an object placed in the field of the Earth’s gravity. Gravitational Fields G = 6.67 x Nm2 / kg2

Grounding a charge: Touching a charged object with a ground removed the charge. The ground is a source of universal neutrality. Static Electricity

Electric Fields An electric field surrounds any object that has a non-zero charge. The direction of the electric field is determined by a positive test charge.

Electric Fields The direction of the electric field is away from the positive charge and toward the negative charge. Electric field lines verify that like charges repel each other and unlike charges attract each other.

Electric fields are vector quantities: MagnitudeDirection Electric Fields q

The direction of the field at any point is in the same direction as the force experienced by a positive test charge placed at that point. Electric Fields

An electric charge Q sets up an electric field in the space surrounding it. q Electric Fields

A second charge q placed near Q experiences a force due to the field generated by charge Q. F Q q Electric Fields

A field strength of 5.00 N/C at a given points means that a point charge q of 1.00 C placed at this point would experience a force of 5 N because of the electric field of Q. 5 N q 1C Electric Fields

2.00 Coulombs  10.0 N 10 N q 2C Electric Fields

15 N q 3C Electric Fields 3.00 Coulombs  15.0 N

The magnitude of the electric field at a certain point is the Force exerted on a charge by the field and depends on the size of the charge located at that point. 3F q 3C Electric Fields

This works the same way with mass in the Earth’s gravitational field. m w = mg Electric Fields

2m w 2 = 2mg = 2w Electric Fields This works the same way with mass in the Earth’s gravitational field.

3m w 3 = 3mg = 3w Electric Fields This works the same way with mass in the Earth’s gravitational field.

Electric field lines - rules: Electric Fields Closely spaced lines indicate a strong field. Lines spaced far apart indicate a weak field. Electric field lines never cross each other.

Field lines point away from positive charges - + Electric field lines - rules: Electric Fields Field lines point toward negative charges

the direction of the electrical force on that charge is the direction of the electrical field. Electric field lines - rules: Electric Fields When a positive charge is placed in an electric field, q1q1 q2q2 F

Using Coulomb’s Law equation, the Electric Field Strength can also be determined by: Electric field strength (F/q) varies with the amount of charge and distance from a source. (N/C) Electric Field Strength When a 1.45 C charge experiences a force of 2.50 x N, the strength of the field is: E = F/q = 2.50 x N 1.45 x C = 1.72 x 10 3 N/C E = F/q = k q/r 2