What are eddy currents? How are these produced? In what sense are eddy currents considered undesirable in a transformer, and how are these reduced in such a device?
Solution
Eddy currents are the circulating currents induced in the body of a conductor when the magnetic flux through it changes.
Production: a time-varying flux (for example from an alternating current) through a solid conductor induces emfs that drive closed-loop currents within the metal.
In a transformer core the alternating flux sets up eddy currents that dissipate energy as heat, lowering efficiency and heating the core — this is undesirable.
Reduction: the core is built from thin iron sheets (laminations) insulated from one another. This breaks the conducting paths, raises their resistance, and so cuts the eddy currents and the heat loss.
Production: a time-varying flux (for example from an alternating current) through a solid conductor induces emfs that drive closed-loop currents within the metal.
In a transformer core the alternating flux sets up eddy currents that dissipate energy as heat, lowering efficiency and heating the core — this is undesirable.
Reduction: the core is built from thin iron sheets (laminations) insulated from one another. This breaks the conducting paths, raises their resistance, and so cuts the eddy currents and the heat loss.
CBSE Class 12 Board · 2006 · All India · Subjective