Transfer of electric energy from one circuit to another without the aid of electrical connections is called

• A. Can cause excessive arcing and heat, and as a result is practical for use only with low voltages/amperages.
• B. Is called capacitance.
• C. Is called mutual energy transfer.
• D. Is called induction.

Answer: (D)

Induction is the transfer of energy between circuits through a changing magnetic field. When current in one circuit varies (as with alternating current), it creates a changing magnetic flux that threads a nearby coil. This changing flux induces an electromotive force in the second circuit, pushing current there even though there’s no direct electrical connection between the circuits. This magnetic-field coupling is the principle behind transformers and wireless power transfer.

This isn’t about energy moving by a spark or through a direct conductor, and it isn’t simply about storing energy in the electric field between conductors (that would be capacitive effects). The hallmark term for this non-contact energy transfer is induction (inductive coupling).