Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

As shown in the diagram below, an infinitely long, thin wire carries a 2 A curre

ID: 1447595 • Letter: A

Question

As shown in the diagram below, an infinitely long, thin wire carries a 2 A current to the right. Calculate the magnetic field strength 5 cm away from the straight wire (ignore the wire loop shown in the figure). A square loop of wire 5 cm on a side is now placed with its top 5 cm below the straight wire, and has a current of 0.5 A driven clockwise through it. Calculate both the magnitude and direction of the net force on the square wire loop. Is there a net torque on the wire loop? Briefly explain how you determined your answer.

Explanation / Answer

Magnetic field due to an infinite wire carrying current is B = 2kI/a

a) B = 2*10^-7 *2 /0.05 = 80*10^-7 T
b) Magnetic field at 5 cm from the wire = B1 = 80*10^-7 T
Magnetic field at 10 cm from teh wire = B2 = 40*10^-7 T

Net force = IL(B1 - B2) = 0.5*0.05*(40*10^-7) = 10^-7 N [towards the wire]
c) there are no out of plane forces on the loop, hence no torque