3. Two identical parallel wires shown with thick lines in Fig. 3 have length L and are at distance a L from each other. These wires are characterized by resistance per unit length equal to Ro (that is, measured in 2/m). They are part of the electric circuit also containing battery with known emf and two resistors with given resistances R and R2. The resistance of the battery and all connectors is negligible. What is magnitude F of the magnetic force these wires exert on each other? Is it the force of attraction or repulsion? Find length L of the wires needed to achieve maximum possible value of F? R ww a R ww Figure 3: Illustration for problem 3.