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# The Physics Behind magnetic strips on Credit Cards

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## Neena Thomas

on 24 April 2015

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#### Transcript of The Physics Behind magnetic strips on Credit Cards

The Physics Behind Magnetic Strips on Credit Cards

By: Neena Thomas

Index
Purpose
To explain the physics behind encoding magnetic strips on credit cards

This stripe is a very thin layer of magnetized material that has information stored on it. This material helps it retain magnetic properties even after an external magnetic field is removed
Physics Law 1:
The current received by the pickup coil goes through signal amplification, and is translated into binary code (which is done by the alternating magnetic fields) so that the signal could be read by a computer.
Main Idea
How exactly is information “encoded” onto a stripe of metallic material?

The stripe acts as a bar magnet. It is made up of very small magnetic particles with each one acting as a bar magnet.

When placed in a very strong external magnetic field, the polarity of the particles is flipped, and information is 'encoded'.
The process of encoding is done by a solenoid.

In a solenoid, current is run through, which creates a change in magnetic flux and in turn creates an induced magnetic field inside the solenoid.
In a given amount of time, changing magnetic field produces voltage, which in turn can create a current in the card reader.

When the card is moved through the reader, change in magnetic flux is produced in one direction.
Physics Law 2: Ohm's Law
This is an extremely simplified explanation of how information is stored on magnetic stripes and received by pickup coils, but these principles of physics are fundamental to understanding the mechanisms behind it.
Project Conclusions
After a number of card swipe tests at varying velocities, the average swipe velocity was in the range of 0.17- 1.8 m/s

The slow swipes were too slow to create a quick enough change in magnetic field, so that no current was induced in the card reader.

For the fast swipes, change in magnetic flux was too rapid to be discerned by the card reader.
Purpose:
To explain the physics behind encoding magnetic strips on credit cards.

Main Idea:
To show how exactly information is 'encoded' onto a stripe of metallic material.

Laws & Applications
:
Importance of laws such as Faraday's law and Ohm's law will be explained in this presentation.

Conclusion and Q & A
Right Hand Rule
Take your right hand, point your thumb in the direction of the current. Picture the current going through a wire, and curl your fingers around the wire. Your four fingers point in the direction of the magnetic field produced by the current.
Works Cited
"Lasers, Technology, and Teleportation with Prof. Magnes." Lasers Technology and Teleportation with Prof Magnes. <http://pages.vassar.edu/ltt/>.

<http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html>.

"Ohm's Law."
<http://www.physicsclassroom.com/class/
circuits/Lesson-3/Ohm-s-Law>.
Full transcript