Question

The circumference and perimeter of circular and rectangular coils are equal.which loop experiences greater torque in a magnetic field on carrying same current

Answer 1

since The circumference and perimeter of circular and rectangular coils are equal,
 2πr =2( l+b)
πr=l+b
circle will always have a larger area than a rectangle having the same perimeter. read here- https://answers.yahoo.com/question/index?qid=20110109112343AA0yVHe
Now Torque T= nIABcosx
where n= no. of turns in the loop
           I= current in the loop 
           A= area of loop
           B= magnetic field intensity
           x= angle between plane of loop and magnetic field
 
Now, since area of circle > area of rectangle
therefore, torque experienced by circular loop >  torque experienced by rectangular loop