Lec10&amp;12-CurrentConductors

Lec10&amp;12-CurrentConductors - ECSE 351...

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ECSE 351 Electromagnetic Fields McGill University – ECE Dept. - Prof. Milica Popovi ć Lectures 10 & 11: Currents and Conductors Objective: we want to be able to: Define electric current and “fit it” in Maxwell equation form, Answer these questions about conductors: 1) how does electrostatic field affect the conductors? 2) how do conductors effect electrostatic field in which they are placed? Introduce the concept of boundary conditions

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Current vs. Current Density z What is electric current? McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic [] Aa m p e r e dQ I dt ==
Current vs. Current Density - what is the MAIN difference that you notice? 22 Aa m p e r e m meter J ⎡⎤ = ⎢⎥ ⎣⎦ ur McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic S IJ S S ∆= =• u ru u u r u u u r Formal definition:

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Current vs. Current Density McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic
Current Density v J v = u ru u r ρ McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic ¾ This is often called convection current density. You can increase it in two ways (how?).

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Current Density v 23 AC m mm s Jv == u ru u r ρ McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic ¾ This is often called convection current density. You can increase it in two ways (how?).
Principle of conservation of charge z Can charges be created? ¾ Only simultaneously + and - , by separation! z Can charges be destroyed? ¾ Only simultaneously, by recombination of + and - ! McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic

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Continuity Equation v J t ρ ∇• =− ur McGill – ECE – ECSE 351 Electromagnetic Fields – Prof. M. Popovic
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This note was uploaded on 01/10/2011 for the course ECSE 351 taught by Professor Davis during the Winter '08 term at McGill.

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Lec10&amp;12-CurrentConductors - ECSE 351...

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