Physics

Problem

A coaxial cable consists of a solid inner conductor of radius

a=2\,\text{mm}

and a concentric cylindrical conducting shell whose inner radius is

b=4\,\text{mm}

and outer radius is

c=6\,\text{mm}

. The inner conductor carries a current of

20\,\text{A}

directed out of the page, uniformly distributed over its cross-section. The outer shell carries an equal return current uniformly distributed over its own cross-section. a. (i) Calculate the magnitude of the magnetic field at a radial distance

r=1\,\text{mm}

from the axis. b. (ii) Calculate

|\mathbf{B}|

r=3\,\text{mm}

. c. (iii) Calculate

|\mathbf{B}|

r=5\,\text{mm}

. d. (iv) Calculate

|\mathbf{B}|

r=8\,\text{mm}

. e. (v) Explain briefly why signal interference is minimised in such a cable construction.

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