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 4.0 A .

How close can a credit card be held to this wire without damaging its magnetic strip?

Answer 1

Magnetic field which can corrupt credit card, B = 1000 gauss

We know that: 1 Gauss = 10^-4 T, So

B = 1000 gauss = (1000 gauss)*(10^-4 T/1 gauss) = 0.1 T

Current through straight wire = 4.0 A

Now magnetic field due to current carrying wire at 'd' distance is given by:

B = *I/(2*pi*d)

d = distance at which magnetic field can corrupt credit card = *I/(2*pi*B)

d = 4*pi*10^-7*4.0/(2*pi*0.1)

d = 8.0*10^-6 m = 8.0 m = closed distance at which credit card can be placed with damaging magnetic strip

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