Test Your EQ (Engineering Quotient)

EQ #13

01/06/2020
Written by Circuit Cellar Staff

Is the signal carried by an “ideal” coaxial cable immune from external electric and magnetic fields? Explain.

Yes, an “ideal” coaxial cable forms a perfect shield against the influence of external fields.

First, consider the fields generated by the signal in the first place. The electric field exists only between the center conductor and the surrounding shield, within the dielectric of the cable. Both the center conductor and the shield have magnetic fields associated with the currents flowing within them, but it’s easy to show that the net magentic field outside the shield is zero.

Thus, the signal in the coaxial cable produces neither type of field outside the shield. Applying the principle of reciprocity, it’s impossible for an external field of either type to affect the signal.

Don't miss out on upcoming issues of Circuit Cellar. Subscribe today!

 
 
Note: We’ve made the October 2017 issue of Circuit Cellar available as a free sample issue. In it, you’ll find a rich variety of the kinds of articles and information that exemplify a typical issue of the current magazine.

Would you like to write for Circuit Cellar? We are always accepting articles/posts from the technical community. Get in touch with us and let's discuss your ideas.

— ADVERTISMENT—

—Advertise Here—

You may also like