Static Electricity Static charges collect on surfaces and remain there until given a path to escape.

What is Static Electricity? Static electricity is the build up of electric charge on the surface of objects. The static charges remain on an object until they are given a path to escape. http://fun-gallery.com/pictures/funny-2/static-electricity-2946/

How do objects get Static Electricity? All matter is made of atoms that contain charged particles – electrons and protons The protons are held tightly in the nucleus (with the neutrons) but the electrons are spinning around the nucleus in orbits http://mahara.org/artefact/file/download.php?file=81503&view=17707

How do objects get Static Electricity? The electrons can leave the atom and go to another atom, leaving one atom positively charged and the other negatively charged.

Protons cannot move!! Static electricity is caused by the movement of the electrons. The protons cannot move. An object becomes positively charged when some electrons are removed!

How do objects get Static Electricity? Usually the number of electrons and protons is the same so that the object is neutral (without charge) Electrons can be transferred from one object to another by friction

How do objects get Static Electricity? When two objects of different materials are rubbed together, one always becomes positively charged and the other becomes negatively charged

Electron Affinity Electron affinity refers to the tendency of a material to hold onto electrons. Different materials have different abilities to hold onto electrons

Electron Affinity In some materials, like acetate, the atoms do not have a strong hold on the electrons, and will lose some electrons when rubbed with a material with a stronger electron affinity

Electron Affinity In some materials, like gold, the electrons are held very tightly, and will steal electrons from other materials with a weaker hold on electrons. Gold acetate

Electrostatic Series A list of some materials listed in order of their electron affinity. The materials at the top of the list have a lower electron affinity than the materials below

Electrostatic Series This means that when two materials are rubbed together, the one that is listed above the other will lose some electrons and become positively charged The material that is below the other will gain those electrons and become negatively charged

Predict the charge Glass and nylon Wood and nylon Steel and Teflon You pet a cat Silk and cotton Glass and cotton

Important fact: no electrons are lost Important fact: no electrons are lost! They are only transferred to another material

The Laws of Electric Charges Objects with a like charge will repel Objects with an unlike charge will attract Neutral objects are attracted to charged objects _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ + + + + + + + + + + + + + + + + + + + + + + + +

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Materials are usually neutral

Why do objects with static charged stick together? When objects become charged they are attracted to neutral objects and to objects with the opposite charge

The rubber balloon was rubbed onto the woolen sweater The balloon took the electrons from the sweater since rubber has a higher electron affinity than wool The negatively charged balloon sticks to the positively charged sweater. The wall is neutral – equal number of electrons and protons

The negatively charged balloon is brought close to the wall The negatively charged balloon is brought close to the wall. The electrons in the wall are repelled by the excess electrons in the balloon and they move away from the balloon leaving the part of the wall closest to the balloon positively charged. The positive wall and the negative balloon are attracted to each other and they stick.

Induced charge separation Occurs when a neutral object comes close to a charged object. The electrons in the neutral object move towards a positively charged object (attracted) Or the electrons move away from a negatively charged object (repelled) This leaves the side of the neutral object with the opposite charge to the charged object

Why dust sticks to your T.V. + + + + + + + + + + + + + + + + + + - + - + +- -+ Neutral dust particle T.V.