Magnetic field from current-carrying wire · CAP 2005 #15
Physics · electromagnetism
Problem
A static magnetic field of about 0.01 T in strength can erase data on the magnetic strip of a credit card. What would be roughly the minimum diameter of a long straight wire carrying a 100 A current for which your card would be safe no matter how close you take it to the wire?
(a) 0.2 mm; (b) 1 mm;
(c) 2 mm; (d) 4 mm.