Week 1 notes
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This 6 page Class Notes was uploaded by Marimann on Saturday August 29, 2015. The Class Notes belongs to PHYS 222 at Iowa State University taught by Lajoie in Fall 2015. Since its upload, it has received 70 views. For similar materials see Intro to classic physics 2 in Physics 2 at Iowa State University.
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Date Created: 08/29/15
Iowa State Physics 222 Week 1 Lecture 1 this class is mostly about electricity and magnetism 0 important info 0 13th edition of university physics 0 register for mastering physics first hw due friday I mp course id is Physics222Fall2015 link with isu net id 0 standards and units 0 lengthtimemass are three fundamental quantities of physics 0 the international system is most widely used system I meters seconds kilogramsetc I prefixes I equations must be dimensionally consistent 0 ex velocitymsdistancemtimess o msms o vectors and scalars o a scalar quantity can be described by a single number a vector quantity has both magnitude and a direction in our book a vector quantity is represented as A39gt a magnitude of a vector is written as A39gt drawing vectors I drawn as an arrow I length of the line shows magnitude I direction of line shows direction 0000 I opposite vectors have equal magnitude adding vectors graphically uses parallelogram or tip to tail method o multiplying a vector by a scalarjust changes the magnitude not the direction F 2 0 components of a vector I adding vectors graphically provides limited accuracy I vector components provide a general method for adding vectors I any vector can be represented with xcomponents and ycomponents AX I 1 I components of a vector can have positive or negative numbers depending on the coordinates system chosen usually left and down are negative I A unit vector has a magnitude of 1 with no units 0 i i hatpoints in the x direction 0 j j hat points in the z direction 0 k k hat points in the z direction l I cross product is always perpendicular to the inputs 0 End of lecture 1 Lecture 2 Electric charge and Coulomb s law classical physics 0 topics that were recognized and welldeveloped before the beginning of the 20th century 0 classical mechanics acous cs thermodynamics optics electromagnetism I electric and magnetic phenomena I single branch because of the intimate connection between the discovered in the early 19th century I electrostatics OOOO 0 electric charges at rest 0 studies 0 stationary electric charges 0 forces between these charges 0 fields produced between these charges 0 Can be applied to slow movina charges 0 slowltthe speed of light 0 So electrostatics can be used for all practical purposes I electrodynamics 0 electric charges in motion I magnetostatics o magnetic poles at rest I an electric charge 0 with rubbing objects acquired some kind of electric charge positive and negative charges likes repel opposites attract force gets weaker with distance increase 0000 o Triboelectric effect I comes from the greek for rubbing but contact is all that is necessary for electrons to be exchanged I after coming into contact a chemical bond is formed between some parts of two surfaces called adhesion and charges move from one material to equalize their electromagnetic potential 0 electric charge and the structure of matter I the particles of the atom 0 negative electron n or 0 positive proton p or o uncharged neutron I protons and neutrons make up the tiny dense nucleus which is surrounded by electrons I the electric attraction between protons and electrons holds the atom together 0 atoms and ions I a neutral atom np or I a positive ion is an atom with nltp lt I a negative ion is an atom with ngtp gt 0 conservation of charge I the proton and electron have the same magnitude charge I the magnitude of charge of the electron or proton is a neutral unit of charge 0 a proton has a charge of e c an electron has a charge of e 0 charge is measured in CoulombsC which is 62421018e I classification of materials 0 charges move depending on the material 0 conductor 0 charges move freely 0 most metals are good conductors o insulator o charges do not move freely 0 most nonmetals are good insulators o semiconductors 0 intermediate their properties change back and forth freely o silicon is a well known semiconductor 0 there is no perfect conductor or perfect insulator I induction 0 a negative rod is able to charge the metal ball without losing any of its own charge through induction Temperary Permanent F39cusitiyely Neutral metal charging charging charged sphere Iy incluctipn hy inclucticun metal sphere I electric forces on uncharged objects 0 the charge within an insulator can shift slightly as a result two neutral objects can exert electric forces on each other 0 ex a charged comb picking up a piece of plastic 0 this is how geckos stick to walls I its hands have tiny hairs with charges which polarize any surface they are on I cars are painted with electric charge 0 positively charged car body o negatively charged paint 0 the paint it attracted to the car evenly o Coulomb s law I FkQ1QZr2rgtr o k899109 Nm2C2 I very similar to gravity Lecture 3 Electric field and forces 0 electric field 0 a charged body produces and electric field in the space around it c we use a small test charge qO to find out if an electric field is present I A and B exert forces on each other body A sets up an electric field e at point P y e is the force per unit charge exerted by a on a test charge at p the field produced by a positive point charge points away from the charge nah 4 the field produced by a negative point charge points toward the charge I 0 a o the electric field and electric field lines for a positive and negative charge O the electric field lines for two charge systems o more formal definition FgtkQ12r2rgtrEgtQ2 O O O k8988 E the electric field created at point one Qzthe point that feels the electric field 0 properties of an electric field 0 O O a vector field that surrounds electric charges exerts a force on other charges strength of the field at a given point is defined as the force that would be exerted on a positive test charge of 1 C placed at that point we can first calculate the total electric field for arbitrary distribution of charges and then forget them once the electric field is known at any point in space we can compute all electrostatic properties for a test charge q placed anywhere 0 charge density 0 O O 0 an electric field is most useful to represent extended charged bodies an infinite rod I EXA21Ts1x I Ey0 a charged plane I Ego2O two oppositely charged planes next to each other I no electric field outside of the planes I one even field from positive to negative between the planes I