Electricity and Magnetism Explore the second of the four fundamental forces in nature –Gravity –Electricity and Magnetism –Weak Nuclear Force –Strong Force Huge effect on everyday life

Electricity and Magnetism The electromagnetic force is what binds electrons to the nuclei of atoms Responsible for all of chemistry When we liberate electrons from individual atoms, we can make them do work for us So, the topic is extremely important if we are to understand the world around us

Electricity and Magnetism Many of the fundamental particles have something we call electric charge We don’t know what this is, we can only describe the results when particles have the property There are two kinds of charges which we call Positive and Negative

Electricity and Magnetism We observe that like charges repel We observe that unlike charges attract The forces are inverse square law forces, just like gravity, but very much more powerful Atoms have a positive nucleus with surrounding negatively charged electrons

Electricity and Magnetism Each electron in an atom is identical to every other electron so they all have the same mass and the same negative charge The nucleus is composed of positively charged protons and uncharged neutrons All protons are identical and the charge of the proton is exactly the same size as the charge of the electron, but it is opposite

Electricity and Magnetism Normal atoms have identical numbers of protons and electrons Atoms with a missing electron are called positive ions Atoms with an extra electron are called negative ions

Conservation of Charge Another important conservation law is Conservation of Charge Add to our set of tools along with Conservation of Energy and Conservation of Momentum We don’t know why, but we observe it to always be true Another deep meaning that isn’t simple

Coulomb’s Law Relationship describing the force between two charged particles Charge is measured in coulombs Force in newtons Distance in meters

Coulomb’s Law One Coulomb is a HUGE charge Takes 6.25 x electrons to amount to this much charge The constant k is 9 x 10 9 Nm 2 /C 2 Shows how huge the electric force really is

Coulomb’s Law

Charge Polarization Make a tiny difference in the average positions of electrons in an atom Distorts electrons like tides on the earth and pulls the nucleus to the right

Electric Field How do things interact with each other when they don’t physically touch? Problem has occupied many great minds When we talked about gravity, we said that Einstein demonstrated that mass distorts spacetime and the bending of spacetime made objects appear to experience a force Can talk about a gravitational field

Electric Field Place a charged particle in spacetime and it creates an electric field Using Coulomb’s Law, we can calculate the force on a test charge at every point in space The force/unit charge is the definition!

Electric Field

Electric Potential Lift an object into the air and we give it gravitational potential energy

Electric Potential Separate a positive charge from a negative charge and give it electric potential energy

Electric Potential Define electric potential as the electric potential energy per unit charge