The magnetic field strength measured in Oersteds (Oe) required to 'flip' the polarity of a bar magnet with two stable polarities.

e.g. place a magnetic particle in a strong magnetic field of the opposite polarity and the particle's polarity will swap (north to south, south to north).

Credit cards and other cards with magnetic strips/stripes are made in a high-engery and a low-energy form. High-energy cards take ~4,000 Oersteds to encode. Low-energy cards require a mere ~300 Oersteds.

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