One is an instrument that uses an oscillating current
in a strong magnetic field, which creates detectable ultrasonic vibrations.
When placed near the tag, this field induces an oscillating current
in the inductive coil on the tag.
When Hertz was performing the experiments that gave him the first glimpse of a photoelectric effect (see 1887), he expected that the oscillating current
he was working with would produce an electromagnetic wave.
By applying a high frequency oscillating current
to a coil, an electromagnetic field is set up within that coil.
We have now defined a magnetic configuration for the AC mode with the wire array (oscillating currents
at variable frequency f and fixed amplitudes [I.sub.1] = [I.sub.4] = 1.4 A and [I.sub.2] = [I.sub.3] = 3.5 A) and the external field ([B.sub.0,y] = 0.3 mT) that (i) holds the neutron spin and (ii) generates an oscillating gradient with the required amplitude to induce resonant transitions between quantum states.
After these events, detached large sponges are commonly found, still alive and intact, between reef spurs on sand or rubble where they slowly erode under the action of oscillating currents