A coil acts like a resistor to AC. The coil can be tuned to be zero resistance to all frequencies but the one frequency you want to block or it can do just the opposite it can block all frequencies but the one you want to allow to pass through. An LC circuit is a tuned circuit. There are AC choke coils that are used for current limiting and their are radio frequency coils.
A toroid may or may not produce a voltage higher than the supply - just like any other coil may or may not produce a voltage higher than the supply.
But in general a toroid is wound on a metallic core that has a higher permeability than air and if the supply (voltage) is turned off abruptly, the magnetic energy contained in the core will collapse quickly and produce a voltage of opposite polarity to the energising voltage.
A toroid may or may not produce a voltage higher than the supply - just like any other coil may or may not produce a voltage higher than the supply.
But in general a toroid is wound on a metallic core that has a higher permeability than air and if the supply (voltage) is turned off abruptly, the magnetic energy contained in the core will collapse quickly and produce a voltage of opposite polarity to the energising voltage.
I used to have to wind toroid's they were rather large, now I understand what was happening.
I think.
We had a voltage of 700v on a cable pass through a toroid, the cable was part of a trolley system. But, during R&D I was told to rap 6 turns down from 8 turns I always thought it was reducing voltage.
My reasoning was the wire is used to deliver voltage and data to the trolley I don't remember a transformer on the trolley. The trolley was fitted with a motor which could turn in both directions. It's been a long time since I worked there but the receiver board controlling the motor actions was a 12v system.
Do you think the toroid was acting as the return of communication from the board as an Ack/Nack from the board sending response to the command completing packet verification?