Two parallel, long wires carry currents i1 and i2 with i1 > i2.
Two parallel, long wires carry currents i1 and i2 with i1 > i2. When the currents are in the same direction, the magnetic field at a point midway between the wires is 10μT. If the direction of i2 is reversed, the field becomes 30μT. The ratio i1/i2 is
(a) 4
(b) 3
(c) 2
(d) 1.
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