The two 10-cm-long parallel wires in the figure are separated by 5.0 mm. for what value of the resistor r will the force between the two wires be 1.26×10−4 n?

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1.3 ohm

Explanation:

length of first wires (L) = 10 cm = 0.1 m

distance of the wires apart (d) = 5 mm = 0.005 m

force between the two wires (f) = 1.26 x 10^{-4} N

force between parallel carrying conductors =

where

        I1 = V1/R1 = 9/2 = 4.5 A

I2 =

I2 = 7A

now we can finally get the resistance from ohms law, V = I x R

R2 = V2/I2 = 9/7 = 1.3 ohm

god i hope this !