The measurement of electric field, and the influence of surface charge, in magnetic stimulation.
A circular magnetic stimulator coil placed perpendicularly to the surface of a large uniform conductor induces surface charge. The resulting electrostatic field reduces the total electric field within the conductor to 58% of the value in the absence of surface charge. The properties of 3 kinds of probe for measuring the effect of a magnetic stimulator are considered. A short dipole electric field probe is the only one which correctly measures the total electric field, including the contribution from any surface charge. A search coil generally gives incorrect results, since it is insensitive to the electrostatic field.
Tofts
P S
PS
Department of Clinical Neurology, Institute of Neurology, London, U.K.
Branston
N M
NM
D004553:Electric Conductivity; D004560:Electricity; D008280:Magnetics