Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electomagnetic Induction

  1. Mar 16, 2005 #1
    When a strip of magnetic material, variably magnetized, is embedded in a plastic card that is moved past a small coil of wire, what happens in the coil. What is a practical application of this?

    I have no idea what this means, I don't understand Physics and my teacher doesn't help either. He actually makes it worse, so most of the time I am lost..I am not asking for much I just need someone to explain what this means and possibly get me going in the right direction for an answer!! Thanks!
  2. jcsd
  3. Mar 16, 2005 #2
    ok so you have a strip of magnetic material...its variably magnetized. This means that the magnetic field is different of different parts of the strip.

    Now what happens when you move the strip past a coil of wire? well we know the strip is magnetized so produces a magnetic field, so really we are asking what happens when a magnetic field moves past a coil...

    Faraday's Law?---->http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html

    have a read of that. Hopefully you have realised what the application is, i mean a magnetised strip on a piece of plastic? thats a credit/bank card. What is the strip doing then? some how when shop assistants read your card by swiping the magnetic strip (which you now know passes a coil of wire) they know that it's your card...

    Have a think about that, and don't be discouraged with physics, even if you think you don't understand the subject, it's always like that with things that are worth learning :)
  4. Mar 16, 2005 #3
    Have at it if you wish:
    ~If a car is made of iron and steel moves over a wide closed loop of wire embedded in a road surface, will the magnetic field of Earth in the loop be altered? Will this produce a curretn pulse?
    ~A model electric train requires a low voltage to operate. If the primary coil of this transformer has 400 turns, and the secondary has 40 turns, how many volts will power the train when the primary is connected to a 120-Volt household circuit?
    ~A transformer has an input of 9 Volts and an output of 36 volts. If the input is changed to 12 volts, what will the output be?
    ~A portable CD player requires 12 volts to operate correctly. A transformer nicely allows the device to be powered from a 120-volt outlet. If the primary has 500 turns, how many turns should the secondary have?
    ~How could you move a conducting loop of wire through a magnetic field without inducing a voltage in the loop?
    ~Why does a transformer require alternating voltage?
    ~Can an efficient transformer step up energy?
    Just a few of the many questions I have left that I don't understand...you dont need to give me answers but if you could break any of them down into 'easy' mode~if there is such a thing~then that would be awesome!
    Last edited: Mar 16, 2005
  5. Mar 17, 2005 #4

    This is called "Swiping your Credit Card."

    There are little wiggles of voltage produced in the coil.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook