Question

5. Suppose you have two current lines separated by 1 m and with 1 A of current flowing in each in the same direction. What is the force per unit length between the wires? Do they attract or repel? Suppose now that you add a third wire with a current of 10 A in the same plane and with the current in the same direction. This third wire is 1 m from one of the original wires and 2 m from the other. What are the directions of the forces acting on the two original wires? Are those two wires pulled apart or pushed together?

Answer 1

The magnetic field on are 2 due to are 1 is given by B = mu_o I_1/2 pi d By the right hand and rule It the current is given by right thumb then the and of the finger given direction of magnetic field. Therefore Direction of magnetic field is perpendicular into the paper. The force experienced per unit length by 2 due 1 is given by F = mu_0/2 pi I_1 I_2/d The direction is given by Fledglings left hand rule where is the thumb, index and middle finger in outstretched thumb - force direction Index - magnetic field direction middle - current It we apply these principle we find the force per unit length on both 1 & 2 is F_21 = F_12 = mu)o/2 pi I_1 I_2/d = 4 pi 10^-7/2 pi N/m = 2 times 10^-7 N/m and both force in attractive ie acting toward the other are