Q. 5

# Consider the situation shown in figure. The straight wire is fixed but the loop can move under magnetic force. The loop will A. remain stationaryB. move towards the wireC. move away from the wireD. rotate about the wire

The closest side of the loop to the straight wire carries a current in the same direction as the straight wire. So there will be an attractive force. And for the opposite side of the loop the current is moving in the opposite direction to that of the straight wire, so there will be a repulsive force. As the closest side shows attractive force and the farthest side shows repulsive force, the attractive force will be dominant. To explain it mathematically, we introduce the expression for force per unit length on each of the wires. Where

F denote the force per unit length,

I1, I2 denote the currents in the two wires,

d is the distance between them

μ0 is the magnetic permeability of free space.

The current in the loop is of same magnitude everywhere. The parallel sides of the loop to the long straight wire will encounter all the force. As the side closer to the straight wire carries a current in the same direction, I1I2 will be positive thus it will encounter attractive force and the opposite side will encounter repulsive force as the, I1I2 is negative as the currents are in opposite directions. We can see that the force is inversely proportional to the distance. As the wire carrying current in the same direction is closer than the wire carrying current in the opposite direction, the attractive force will be greater than the repulsive force. The other two sides will experience forces of equal amplitude but opposite directions and thus will cancel each other out. Thus the loop will move towards the wire. Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos  Magnetic field due to current carrying straight wire37 mins  Magnetic field due to current carrying circular loop36 mins  Interactive Quiz on Magnetic field due to straight wire & circular loop41 mins  Gain Confidence on Magnetic Effects of Current with Questions41 mins  Equation of electric and magnetic field52 mins  Magnetic force on moving charge particle in magnetic field | Quiz32 mins  Magnetic force on moving charge particle in magnetic field44 mins  Superfast Revision of Potential & Potenial Energy (Theory + Interactive Quiz)47 mins  Few Applications of Gauss's law54 mins  Electric field inside cavity37 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation view all courses 