Lecture 06 - Electric field lines

# Lecture 06 - Electric field lines - EXAMPLE: Ring Below is...

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1 Lecture 6 Electric fields in dielectrics and conductors. Electric field lines. EXAMPLE: Ring Below is a ring of radius R with uniform linear charge distribution λ . Find the electric field along the z -axis. x P y d θ d q = λ Rd r =+ 22 Rz P 2 dq dE k = G = + cos ϕ = G λθ = + + P Cylindrical symmetry: only E matters φ zRd () 3/2 = + 2 , net 0 zR Ek d π = + 2 πλ = +

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2 From the ring to the charged disk… Disk of radius R with uniform surface charge density σ can be thought of as made of rings of radii r = 0 to = and linear charge density dr. πσ = disk 3/2 0 2 zr Ek d ⎡⎤ ⎢⎥ =− 1/2 1 2 kz ( ) + 22 rz ( ) + ⎣⎦ 0 () ⎛⎞ ⎜⎟ + ⎝⎠ 11 2 z + 21 k Rz ε + 0 1 2 … and to the infinite plane Take the limit −= lim 1 Uniform electric field ! (Does not depend on distance) ( ) →∞ + 00 Electric field in conductors • The electric field inside a conductor in equilibrium is always zero. If 0 0 0 motion of charges (conductor, charges can move) EFa ≠⇒ ≠⇒≠ non equilibrium • The electric field right outside a conductor
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## This note was uploaded on 09/21/2011 for the course PHYS 222 taught by Professor Johnson during the Spring '07 term at Iowa State.

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Lecture 06 - Electric field lines - EXAMPLE: Ring Below is...

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