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Physics 3:  Introduction to Electricity & Magnetism 

<<<  Induced Magnetic Field.    Ampere's Law  >>>

Javier Montenegro Joo

jmj@VirtualDynamics.Org

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(1) A long straight wire of radius R transports an electric current. Calculate the radial distance where the induced magnetic field due to this current, reduces to a half of its maximum value. (a) Out of the wire  (b) inside the wire.

Solution

The maximum induced magnetic field due to an electric current in a wire, is at the surface of the wire.  This is valid for both magnetic fields, exterior and interior.  In this problem the surface of the wire is at  r = R.

The magnetic field induced by a current in a wire is: 

 

EduVirtualLab about oscillations in a rectangular membrane.-

https://www.researchgate.net/publication/318779600_Virtual_Lab_to_run_experiments_of_Oscillations_of_a_Stretched_Rectangular_Membrane

 

 
(2) The propulsion system of an interstellar-travel vessel includes a long, straight, solid, cylinder of radius R.  The cylinder leads lengthwise an electrical current I whose density is  J = A r,  A = Const.  Determine: (a) the constant A  (b) the magnetic field in r ≤ R  (c) the magnetic field in r ≥ R.    

Solution.-

 

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