lecture5

# Lecture5

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Unformatted text preview: Now through this Gaussian (closed) surface we can apply Gauss’s Law d d d Physics 2B - Summer Session 2 - C. Palmer Q August 8, 2013 31   What is the electric flux through the closed cubic surface? What is the electric flux through a single side? A)  Q/ε0; Q/(6ε0) B)  0; Q/(6ε0) C)  Q/ε0; Q/(3ε0) D)  0; 0 d d d Physics 2B - Summer Session 2 - C. Palmer Q August 8, 2013 32   What is the electric flux through the closed cubic surface? What is the electric flux through a single side?   Each side has the same flux A)  Q/ε0; Q/(6ε0) C)  Q/ε0; Q/(3ε0) D)  0; 0 d d B)  0; Q/(6ε0) d Physics 2B - Summer Session 2 - C. Palmer Q August 8, 2013 33   We have an infinite plane (z=0) which is charged with charge density σ [C/m2] > 0. What is the electric field throughout space?   What does the electric field look like?   Where is the symmetry?   We want to use Gauss’s Law to find the electric field.   What sort of shape can we use to simplify the electric flux? Physics 2B - Summer Session 2 - C. Palmer August 8, 2013 34   We have an infinite plane (z=0) which is charged with charge density σ [C/m2] > 0. What is the electric field throughout space?   What does the electric field look like?   Recall ring of charge   Same symmetry   Imagine plane as series of rings   Electric field only perpendicular to plane Physics 2B - Summer Session 2 - C. Palmer August 8, 2013 35   We have an infinite plane (z=0) which is charged with charge density σ [C/m2] > 0. What is the electric field throughout space?   We know the electric field at distance, d, from the surface is:   same in a parallel plane   perp to the charged plane Physics 2B - Summer Session 2 - C. Palmer August 8, 2013 36   We have an infinite plane (z=0) which is charged with charge density σ [C/m2] > 0. What is the electric field throughout space?   The Gaussian Surface we use should have a normal which is EITHER:   Parallel to the field   Perpendicular to the field Physics 2B - Summer Session 2 - C. Palmer August 8, 2013 37   We have an infinite plane (z=0) which is charged with charge density σ [C/m2] > 0. What is the electric field throughout space?   The cylinder to the right satisfies this criteria.   The top and bottom are parallel.   The side is perpendicular. Physics 2B - Summer Session 2 - C. Palmer August 8, 2013 38 Φ Elec = ∫ QEnclosed E ⋅ dA = ε0 Left hand side E ⋅ dA = ∫ ∫ E (d ) dA Cylin der Top +∫ E (− d ) dA + ∫ E ⋅ dA Bottom Si de = E (d )∫ Top dA + E (− d )∫ Bottom = E (d ) * A + E (− d ) * A dA Right hand side QEnclosed σ A = ε0 ε0 = 2 E (d ) * A Physics 2B - Summer Session 2 - C. Palmer August 8, 2013 39 Φ Elec =...
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## This note was uploaded on 09/10/2013 for the course PHYS 2B 2b taught by Professor Hirsch during the Summer '10 term at UCSD.

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