Eddy current damping describes which effect on oscillations?

• A. The decreased amplitude of oscillations by the interaction of magnetic fields; in a vertical card magnetic compass, eddy currents oppose the magnet's flux and reduce oscillations
• B. An increase in oscillation amplitude due to electrical resonance
• C. A dampening method using air jets
• D. A dampening method using friction in bearings

Answer: (A)

Eddy current damping is an electromagnetic braking effect where a conductor moving in a magnetic field experiences circulating currents that oppose the motion. These eddy currents create their own magnetic fields that oppose the change in the external flux, producing a braking force that converts kinetic energy into heat in the metal and reduces the oscillation amplitude. In a vertical card magnetic compass, as the card swings within the field, the changing flux induces eddy currents in the card. The resulting magnetic interaction opposes the magnet's flux and slows the card, damping the oscillations. This non-contact damping relies on electromagnetic induction rather than mechanical friction or airflow, so it naturally reduces motion rather than increasing it.