Nanotechnology-Enabled Sensors

2.3 Physical Effects Employed for Signal Transduction 51
Fig. 2.23 A schematic of the GMR effect after and before applying the magnetic
field.
2.3.17 Faraday-Henry Law
The Faraday-Henry law is a fundamental law of electromagnetism, and
expresses that an electric field is induced by changing the magnetic field
(Fig. 2.24). Michael Faraday and Joseph Henry both independently discovered
the electromagnetic phenomenon of self and mutual inductance.
Their work on the magnetically induced currents was the basis of the electrical
telegraph, which was jointly invented by Samuel Morse and Charles
Wheatstone later on. Early acoustic sensors and devices (such as microphones),
analogue current/voltage meters, and reed-relay switches make
use of this effect.