Claim-Evidence-Reasoning from Electric and Magnetic Forces Scenario

Many hotels now use key cards to access their rooms. Key cards are more cost-efficient and secure than traditional keys. In a magnetic strip card, the strip is made of tiny iron-based pieces in a plastic film. The pieces are very small bar magnets that can have their polarity changed to either north or south pole directions. When the card is blank, all of the magnets are polarized in the same direction. Through a process called flux reversal, the polarity is changed so that it can be used in the reader. Since the process creates either N-N or S-S polarization, the card can easily be used in correspondence with the binary code system for computers.

Prompt

Write a scientific explanation that explains how magnetism is used to create a key card that only opens one room.