What is a primary advantage of using a toroidal core instead of a solenoidal core in an inductor?
Why A toroid is a closed magnetic loop, so the flux path never leaves the high-permeability core material. That self-shielding keeps stray field from coupling into nearby circuits and keeps outside fields from coupling in, which means toroids can be mounted close together without shields. A solenoid (rod or air-wound coil) has an open path, so its flux must return through the surrounding air and sprays out into the rest of the circuit.
Watch out The choice about easier coupling into other components describes the open solenoid, and it is a drawback rather than an advantage; toroids actually have high Q and low loss, not greater hysteresis or lower Q.
Toroid = closed loop = self-shielding. The field stays home in the donut.