An 8.00-cm-long piece of wire is formed into a square,and carries a clockwise current of 0.150 A.The loop is placed inside a solenoid,and the plane of the loop is perpendicular to the solenoid's magnetic field.The solenoid carries a counterclockwise current of 17.0 A,and has 25 turns per centimeter.What is the force on each side of the loop?
A)1.07E-5 N
B)6.41E-4 N
C)1.60E-4 N
D)4.27E-3 N

Question

Quizplus · Accepted Answer

The magnetic field created by the solenoid inside it can be given by using the formula B=μnI where n is the number of turns per unit length and I is the current passing through it. Thus, the magnetic field at the center of the solenoid can be given by B=μnI= 4π×10^-7 ×25×17.0=6.73×10^-3 T (Tesla).
As the loop is perpendicular to the magnetic field, each side of the loop experiences a magnetic force given by F=ILB where L is the length of the wire (side of the square in this case) carrying the current. Since the current is in clockwise direction as seen from one end, the direction of the magnetic force on each side of the loop will be upwards. Thus, the magnitude of the force experienced by each side can be given by F=ILB= 0.150×8.00×6.73×10^-3= 8.08×10^-4 N. 
Therefore, the best choice is C) 1.60E-4 N, as it is the force experienced by each side of the loop.

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