Credit-Card Magnetic Strips Experiments carried out on the television show Mythb

Question

Credit-Card Magnetic Strips Experiments carried out on the television show Mythbusters determined that a magnetic field of 1000 gauss is needed to corrupt the information on a credit card's magnetic strip. (They also busted the myth that a credit card can be demagnetized by an electric eel or an eelskin wallet.) Suppose a long, straight wire carries a current of 7.0 A. How close can a credit card be held to this wire without damaging its magnetic strip? Express your answer using two significant figures.

Explanation / Answer

1000 gauss = 0.1 T

As we know

B = (µ/2)I/r

Therefore

0.1 = (2*10^-7)*(7/r)

r = 0.000014 m

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