Review – Parts of the AtomAtomic Particles Proton Positive charge Neutron No charge Electron Negative charge
Structure of the atom Can you identify the particles?
“Electricity” – which particledoes it sound like?
Electricity Electrons Electricity is the MOVEMENT of electrons
Why Electrons? Protons usually don’t move They are stuck in the nucleus with the neutrons Electrons ORBIT around the nucleus They can be moved out of their orbits, away from the nucleus
Charge CHARGE is the measurement of EXTRA PROTONS or EXTRA ELECTRONS an object has. A POSITIVELY CHARGED object has MORE PROTONS than electrons. A NEGATIVELY CHARGED object has MORE ELECTRONS than protons.
Separating Charges What do we mean when we say “separating charges?”Remember: Electricity is the MOVEMENT of ELECTRONS
Separating Charges cont. Atoms usually have the same number of PROTONS ( + positive charge) and ELECTRONS ( - negative charge) The positive and negative charges balance, so the atom has a NEUTRAL CHARGE ADDING or REMOVING electrons changes the charge of the atom ADDING electrons makes the charge NEGATIVE REMOVING electrons makes the charge POSITIVEThis is what we mean when we say “separating charges.”*A charged atom is called an ION
Separating Charges cont.How Do We SeparateCharges? How can we move electrons from one place to another? FRICTION is one way to separate charge. What is FRICTION?
Separating Charges cont.Friction FRICTION is rubbing two objects together. When two objects are rubbed together, some electrons move from one object to the other object. This separates the charges of the atoms in the surfaces of the objects. The surface of one object becomes POSITIVELY charged, and the surface of the other object becomes NEGATIVELY charged.
Static Electricity When electrons are moved from one object to another object by friction, STATIC ELECTRICITY is the result STATIC (adj) = stays in one spot Once the charge has moved from one object to the other, it stops moving.
Static Electricity cont.Insulators and Conductors Materials like glass, plastic, rubber, and wood are good at collecting electrons in a static charge. These materials are called INSULATORS Materials like metal and water are NOT good at collecting electrons in a static charge. These materials are called CONDUCTORS (MORE ON THIS LATER)
Static Electricity cont. Once electrons have been transferred from one object to another, we can say one object is POSITIVELY CHARGED and the other object is NEGATIVELY CHARGED. What do OPPOSITELY CHARGED PARTICLES do?
Static Electricity cont.EXPERIMENT! What does the balloon ATTRACT? What does it REPEL?
Static ElectricityExperiment Results The balloon was NEGATIVELY charged, so it ATTRACTED anything with a POSITIVE charge It REPELLED anything with a NEGATIVE charge. This illustrates the LAW OF CHARGES!
…but what about neutralcharges? Neutrally charged objects (objects with no charge) are attracted to objects with POSITIVE and NEGATIVE charges. More on this later!
The Triboelectric Series Some materials are better at holding onto electrons, and some materials are better at giving away electrons. The TRIBOELECTRIC SERIES ranks materials based on their affinity for electrons.
Triboelectric Series cont. ALL materials fall somewhere on the triboelectric series. Example using a few different materials:Materials at the TOP of the listgather more electrons than thoseat the bottom.
Law of Conservation of Charge Charge is only transferred. It just moves between objects.
Both the copper and the glass have NEUTRAL CHARGE. They each have 6 units of electrons. What happens if you rub them together? COPPER GLASS 6e 6e
Using the triboelectric series, we see thatcopper gathers more electrons than glass.Using the Law of Conservation of Charge, wesee that the total charge between the twostays the same. COPPER 2e GLASS 8e 4e
The glass loses 2 units of electrons, and so it now has a positive charge. The copper gains those 2 units of electrons, and so it now has a negative charge.
Conductors and Insulators CONDUCTORS let electrons to flow easily between atoms, or between molecules. INSULATORS do not let electrons flow easily between atoms, or between molecules. Can you remember some examples of conductors and insulators?
Conductors When a charge is transferred to an object made from a conductive material, the charge spreads through the object.
Insulators When a charge is transferred to an object made from an insulating material, the charge does not move. This is why insulators are good for demonstrating static electricity. Static = does not move
Conductors vs. Insulators Conductors have an atomic structure that lets electrons move in a clear path. Insulators have an atomic structure that does not allow electrons to move in a clear path.
Polarization Polarization means to separate into opposites. When a charged object is placed on an oppositely charged (or neutrally charged) object, both objects will become polarized. This means that their opposite sides will have opposite charges.