Question

Monopolar needle electrode has a coating of______________ material over the stainless steel wires which are bare only at the tips.

(a) carbon

(b) calcium

(c) teflon

(d) sodium

This question was addressed to me by my college professor while I was bunking the class.

This interesting question is from Transmission of Analog Physiological Signals Over Telephone topic in division Biomedical Telemetry of Biomedical Instrumentation

Answer 1

The correct option is (c) teflon

Easy explanation: The wire is bare only at the tip. The monopolar needle electrode consists of a teflon coated stainless steel wire.  It is found that after the needle has been used a number of times, the teflon coating will recede, increasing the tip area. The needle should be discarded when this happens.