In electroconvulsive therapy an electric current is passed t

In electroconvulsive therapy an electric current is passed through the brain of a severely depressed patient and, surprisingly, the patient often feels better. Somewhat similar results arc obtained with the technique of Trans-Cranial Magnetic Stimulation (TCM) in which the applied potential difference is replaced by a constant magnetic field a time-varying magnetic field a constant electric field c) a time-varying electric field.

Solution

The current passing through the coil produces the magnetic field as per Biot -Savart\'s law. Trans Carnial Magnetic stimulation is achived by suddenly discharging the cuurent through a large capacitor to produce a pulsed magnetic fields of 2 -3 tesla. This magnetic field pulse is focussed on the desired region to depolarize or hyper polarize the neurons .The magnetic flux density pulse generated by the current pulse produces an electric field as per Faraday\'s law, which causes a change inthe transmembrane current which leads to the depolarizing or hyper polarizing the neuron by firing an action potential. hence time variying magnetic field is required