Two long, straight, parallel wires 7.2 cm apart carry currents of equal magnitude I. They repel each other with a force per unit length of 4.2 nN/m. Find the current I.

current I = 38 mA

Explanation:

given data

distance r = 7.2 cm

repel each other force per unit length \frac{F}{l} = 4.2 nN/m

solution

we know 2  wire is parallel and when current flow through these wire they exert force each other due to magnetic field

and current I(1) = I(2)   ................1

so

    ..................2

put here value

4.2 × =    

solve it we get

I = 0.038884 A

current I = 38 mA

the answer is neither ball has a charge.

because if they were both positively charged, they will repel each other.

if they were positively and negatively charged, they will seek.