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# Static Electricity

## on Jan 02, 2011

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## Static ElectricityPresentation Transcript

• Static Electricity
• all matter is made of atoms
• atoms contain smaller particles: protons , neutrons and electrons
• some of these particles have an electric charge:
Atomic Structure & Electric Charge
• orbiting the nucleus negative (-) electron nucleus no charge (0) neutron nucleus positive (+) proton Location Electric Charge Particle
• If an object has more electrons than protons, it is negatively charged.
Electric Charge # protons: 8 # electrons: 12 # protons < # electrons therefore, overall charge = negative
• if an object has more protons than electrons, it is positively charged
Electric Charge # protons: 8 # electrons: 5 # protons > # electrons therefore, overall charge = positive
• If an object has an equal number of protons and electrons, the object is neutral
Electric Charge # protons: 8 # electrons: 8 # protons = # electrons therefore, overall charge = neutral
• Electric Charge + — Law of attraction: opposite charges attract
• Electric Charge Law of repulsion: like charges repel + — + —
• Electric Charge A charged object and a neutral object will attract each other 0 0 + —
• Electrons can be transferred from one object to another.
• For example, a neutral or positively charged object will become negatively charged if it gains electrons.
Electric Charge
• Similarly, a neutral or negatively charged object will become positively charged if it loses electrons.
Electric Charge
• Only electrons (negative charges) are capable of moving from one object to another!
• Protons ( positive charges) stay in place.
Electric Charge
• Different substances have different abilities to hold on to electrons
• the tendency of a substance to hold on to the electrons is called electron affinity
Electron Affinity
• Electron Affinity human skin rabit fur acetate glass human hair nylon wool cat fur silk paper cotton wood amber rubber balloon vinyl polyester ebonite + - tendency to lose electrons tendency to gain electrons
• Conductivity is the ability of materials to allow electrons to move freely
• Materials that hold on to their electrons and do not allow them to move easily are called electrical insulators
• Materials that allow electrons to change positions are called conductors
Conductors & Insulators
• Insulators In an insulator, the electrons (-) are bound tightly to the nuclei (+) so they resist movement + — + — + — + — + — + — + —
• Common Insulators
• Conductors In a conductor, the electrons are not as tightly bound to the nuclei and can therefore move away from the nuclei + — + — + — + — + — + — + —
• Common Conductors
• The electric charge that builds up on the surface of an object is called a static charge
• The charges are “static” because they remain in one location on the surface of the object until they are given a path to escape
Static Electricity
• Static Electricity and Friction
• All solid materials are charged by the transfer of electrons
• When two objects rub together, the force of friction can remove electrons from one object and transfer them to the other object
• As one object loses electrons, the other object gains them
Static Electricity and Friction
• New electrons are not being created , they are just being rearranged
Static Electricity and Friction
• Static Electricity