Lecture 1 - Electromagnetism in one slide Electric charges q establish electric fields E everywhere in space An electric charge experiences an

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Electromagnetism in one slide • Electric charges q establish electric fields E everywhere in space. • An electric charge experiences an electric force F E =q E , where E is the electric field at the charge’s position, and q is the magnitude of the charge. • Moving electric charges result in electric currents; electric currents establish magnetic fields B everywhere in space. • A moving charge q experiences a magnetic force F B =q v × B , with v the velocity of the charge and B the magnetic fields at the location of the charge. • Magnetic fields can also be established by time-varying electric fields. Likewise, electric fields result from time- varying magnetic fields. These coupled effects produce electromagnetic waves.
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Electric charge Protons possess a charge q p =+e , electrons q e =-e , with e= 1.6 × 10 -19 Coulomb(C). • Experimentally |q p +q e |/e <10 -21 , the electron charge is equal and opposite the proton charge. • The total charge is Q=(N p -N e )e , with N p ,N e the number of protons,electrons. • Ordinary matter is electrically neutral: Q= 0 , so N p =N e . • In a typical material, water, there are ~10 6 C/mole, or 5 × 10 4 C/cm 3 of proton charge and an equal amount of electron charge.
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Let’s try the clickers How many protons are to needed for 1 C of charge? A. 1.6×10 -19 B. 1 C. 6.2×10 18 D. 6.0×10 25
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The E-field of 1 charge •This is the basic building block of electric fields: – The first factor is the charge Q . Fields point away from positive charges and towards negative charges. – The second factor k=1/4 πε 0 9 × 10 9 Nm 2 /C 2 is, as we shall see, a measure of how strong electric forces are. The peculiar way of writing k in terms of another constant ε 0 =8.85 × 10 -12 C 2 /Nm 2 will be explained later. – The third factor
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This note was uploaded on 05/11/2010 for the course PHY 214 taught by Professor Timothybolton during the Spring '10 term at Kansas State University.

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Lecture 1 - Electromagnetism in one slide Electric charges q establish electric fields E everywhere in space An electric charge experiences an

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