A toroid is similar to a solenoid, in that they both are electromagnets that are from wires carrying currents. The two devices differ in the shape of their design. A solenoid is frequently formed into helical coils with pieces of metal inside, whereas a toroid is circular (like a doughnut). The circular shape of the toroid allows for it to create a magnetic field within itself, while not leaking outside the toroids. The inner part of the ring will be more magnetic than the outside sections. As the radius of the circle becomes larger the magnetic field will decrease.

Just like solenoids, a toroid is also considered an inductor. An inductor creates currents in nearby coils. Altering magnetic fields can induce a voltage in adjacent wires (Faraday’s Law of Induction). A toroid is also known to possess  self-inductance, which is classified as a type of resistance. A toroids can fight changes/resist its self-produced current. This is the case when making it larger or smaller. Self-inductance strength largely depends on the number of coils for the toroids, as well as the AC source.

When compared to solenoids; a toroids is more efficient when creating required inductances. Toroids also require fewer turns than a solenoid. Considering magnetic fields are maintained within the toroids, transformers can be installed near other electrical components.

Related Reading about Toroid Coils

• Learning About Toroidal Transformers
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• Uncommon Toroid Benefits
• Why do Toroidal Transformers Stand Out from Other Transformers