The right and left end wires of two circuits are separated b

The right and left end wires of two circuits are separated by a distance d = 10 mm.

If L = 1 cm, V1 = 19 V, V2 = 8 V, R1 = 4 and the magnetic force between the circuits is F = 10 N, then what is the resistance (in ohms) of R2?

Solution

the magnetic force is,

    F/L = u₀I1I2/2*pi*d

    F/L = u₀[V1/R1][V2/R2]/2*pi*[10X10^-3]

    [10*10^-6]/[0.01] = [4*pi*10^-7][19/4][8/R2]/2*pi*[10X10^-3]

hence, the resistance R2 is,

       R₂ = 0.76