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# Currents in a Metal Wire and Shell.?

A solid conductor with radius 0.8mm is supported by insulating disks on the axis of a conducting cylindrical shell with inner radius 9.1mm and outer radius 9.9mm . The central conductor and the shell carry currents I1 = 5.4A and I2 = 1.9A respectively, and in the same direction. The currents are distributed uniformly over the cross sections of each conductor.

1.) Calculate the magnitude of the current density in the inner wire.

2.) Calculate the magnitude of the current density in the outer shell.

by ?
Member since:
November 01, 2010
Total points:
112 (Level 1)

Current density(J) is the current(I) per area(A).
So J=I/A, however your A is the area of the circle. So we use the equation pi*r^2=A
J=I/pi(r^2)
Its in mm so I will change it just by dividing by a thousand.

1) The inner wire has a radius of 0.8/1000, so J=5.4/(pi*(0.8/1000)^2

2) For the outer shell is J=1.9/(pi*[(9.9/1000)^2-(9.1/1000)^2])
thanks

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