sentences:  The magnetic field is about the same strength as an MRI, and the pulse generally reaches no more than 5 centimeters into the brain, unless using a modified coil and technique for deeper stimulation.From the Biot–Savart law,
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  it has been shown that a current through a wire generates a magnetic field around that wire.Transcranial magnetic stimulation is achieved by quickly discharging current from a large capacitor into a coil to produce pulsed magnetic fields between 2 and 3 Tesla in strength.