Electrostatics (Static Electricity)

Electrostatics – The study of electric forces and the transfer of electric charge

Makeup of an atom What are the 3 main subatomic particles that make up the atom? What are their charges and where are they located in the atom? Proton ( + ) nucleus (p+) Neutron (neutral) nucleus Electron ( - ) outer shells (e-) Which subatomic particle can be easily removed from the atom? Electron

4 Fundamental Forces Gravity Electromagnetic Force Weak Force Strong Force

The electron is most easily removed from the atom because it is attached to the atom via the electromagnetic force, which is significantly weaker than the strong force that bonds the nucleus together. What happens if you remove a proton from the nucleus?

Ok, that was an exaggeration… But removing protons from the nucleus is a process called fission and causes a release of energy. This is the basic idea behind the atomic bomb. Removing protons from one atom or on a small scale will not result in anything that noticeable.

Electric Charge (q or Q) Measured in Coulombs (C) Charles Coulomb (1736-1806) French Physicist 2 Types Positive Negative They could have been called anything, they are just opposites of one another.

Conservation of Charge Charge is always conserved. If atom A loses an electron then atom B must gain that electron. Atom A becomes positively charged. Atom B becomes negatively charged.

So if the charge of the glass rod is now +4C then the charge of the silk is –4C.

Charged Objects and Their Interactions What does it mean to be… Positively charged – object has more protons than electrons Negatively charged – object has more electrons than protons Neutral – object has equal number of protons and electrons

Demo Decide if the answer for each statement below is either attract, repel, or do nothing. Opposite charged objects (+ and –) will (attract, repel, or do nothing) Like charged objects (+ and + or – and –) will (attract, repel, or do nothing) Positive objects and neutral objects will (attract, repel, or do nothing) Negative objects and neutral objects will (attract, repel, or do nothing)

In case you missed the Demo:

Conductors and Insulators conductors – material that allows the flow of electric charge - If there is a surplus of negative charge the electrons will spread out as much as possible. Examples: metals, impure water

Insulator – material that impedes the flow of electric charge - If there is a surplus of negative charge the charge will remain where it was placed. examples: wood, glass, dry human skin, rubber, plastic, pure water

POLARIZATION Polarization is a redistribution of electrons in a neutral object when a charged object is brought near the neutral object. - In conductors the electrons will shift and detach from their atoms. - In insulators the electrons will shift but stay attached to their atoms.

Before After + + _ + - + + - + +- + - + + + + _ + - + Example: A positive rod is brought near a neutral metal sphere. Draw charge diagrams to show what happens to the sphere. Before After + + _ + - + + - + +- + - + + __ + + _ + - + Because the sphere is a conductor the electrons can detach from the from the protons and are attracted to the positive . The protons do not move!!!

Example: A negative rod is brought near a neutral plastic sphere Example: A negative rod is brought near a neutral plastic sphere. Draw charge diagrams to show what happens to the sphere. Before After - + - - + - - - + -+ - + - + - - - Because the sphere is an insulator the electrons cannot detach from the from the protons. The just shift to repel the negative rod. The protons do not move!!!