Question

Electromagnetic coupling cannot be reduced by ___________

(a) shielding

(b) wire twisting

(c) multiple grounding

(d) common grounding

I had been asked this question in an interview for internship.

This intriguing question originated from Biomedical Signal Analysis and Processing Techniques topic in chapter Recording System of Biomedical Instrumentation

Answer 1

Right answer is (c) multiple grounding

For explanation: Having multiple grounds in a single circuit increases the electromagnetic coupling effect by producing ground loop which may generate so much noise that it may completely obscure the useful signal. Thus, the electromagnetic coupling is reduced by shielding, wire twisting and proper grounding which provide a balanced signal pair with satisfactory noise rejection characteristics.