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Electromagnetic Theory. G. Franchetti , GSI CERN Accelerator – School Budapest, 2-14 / 10 / 2016. Mathematics of EM. Fields are 3 dimensional vectors dependent of their spatial position (and depending on time). Products. Scalar product. Vector product. The gradient operator.
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Electromagnetic Theory G. Franchetti, GSI CERN Accelerator – School Budapest, 2-14 / 10 / 2016 G. Franchetti
Mathematics of EM Fields are 3 dimensional vectors dependent of their spatial position (and depending on time) G. Franchetti
Products Scalar product Vector product G. Franchetti
The gradient operator Is an operator that transform space dependent scalar in vector Example: given G. Franchetti
Divergence / Curl of a vector field Divergence of vector field Curl of vector field G. Franchetti
Relations G. Franchetti
Flux Concept Example with water v v v G. Franchetti
v v Volume per second or v θ v L G. Franchetti
Flux θ A G. Franchetti
Flux through a surface G. Franchetti
Flux through a closed surface: Gauss theorem Any volume can be decomposed in small cubes Flux through a closed surface G. Franchetti
Stokes theorem Ex(0,D,0) y Ey(D,0,0) Ey(0,0,0) x Ex(0,0,0) G. Franchetti
for an arbitrary surface G. Franchetti
How it works G. Franchetti
Electric Charges and Forces Two charges + + + + - - - - Experimental facts G. Franchetti
Coulomb law G. Franchetti
Units System SI Newton Coulomb C2 N-1 m-2 Meters permettivity of free space G. Franchetti
Superposition principle G. Franchetti
Electric Field G. Franchetti
force electric field G. Franchetti
By knowing the electric field the force on a charge is completely known G. Franchetti
Work done along a path work done by the charge G. Franchetti
Electric potential For conservative field V(P) does not depend on the path ! Central forces are conservative UNITS: Joule / Coulomb = Volt G. Franchetti
Work done along a path B work done by the charge A G. Franchetti
Electric Field Electric Potential In vectorial notation G. Franchetti
Electric potential by one charge Take one particle located at the origin, then G. Franchetti
Electric Potential of an arbitrary distribution set of N particles origin G. Franchetti
Electric potential of a continuous distribution Split the continuous distribution in a grid origin G. Franchetti
Energy of a charge distribution it is the work necessary to bring the charge distribution from infinity More simply More simply G. Franchetti
In integral form Using and the “divergence theorem” it can be proved that is the density of energy of the electric field G. Franchetti
Flux of the electric field θ A G. Franchetti
Flux of electric field through a surface G. Franchetti
Application to Coulomb law On a sphere This result is general and applies to any closed surface (how?) G. Franchetti
On an arbitrary closed curve q2 q1 G. Franchetti
First Maxwell Law integral form for a infinitesimal small volume differential form (try to derive it. Hint: used Gauss theorem) G. Franchetti
Physical meaning If there is a charge in one place, the electric flux is different than zero One charge create an electric flux. G. Franchetti
Poisson and Laplace Equations and As combining both we find Poisson Laplace In vacuum: G. Franchetti
Magnetic Field There exist not a magnetic charge! (Find a magnetic monopole and you get the Nobel Prize) G. Franchetti
Ampere’s experiment I1 I2 G. Franchetti
Ampere’s Law dl all experimental results fit with this law I2 I B F G. Franchetti
Units [Tesla] From From follows To have 1T at 10 cm with one cable I = 5 x 105 Amperes !! G. Franchetti
Biot-Savart Law dB I From analogy with the electric field G. Franchetti
Lorentz force A charge not in motion does not experience a force ! B v F + No acceleration using magnetic field ! G. Franchetti
Flux of magnetic field There exist not a magnetic charge ! No matter what you do.. The magnetic flux is always zero! G. Franchetti
Second Maxwell Law Integral form Differential from G. Franchetti
Changing the magnetic Flux... Magnetic flux h Following the path L G. Franchetti
Faraday’s Law integral form valid in any way the magnetic flux is changed !!! (Really not obvious !!) G. Franchetti
for an arbitrary surface G. Franchetti
Faraday’s Law in differential form G. Franchetti