AP EAMCET202124 Aug 2021Evening ShiftPhysicsMagnetic Effects of CurrentActual
A toroid of n turns, mean radius R and cross-sectional radius a carries current I . It is placed on a horizontal table taken as x y -plane. Its magnetic moment m
Options
- Ais non-zero and points in the z-direction by symmetry
- Bpoints along the axis of the toroid (m=m )
- Cis zero, otherwise there would be a field falling as 1 r^3 at large distances outside the toroid
- Dis pointing radially outwards
Correct answer
C. is zero, otherwise there would be a field falling as 1 r^3 at large distances outside the toroid
Step-by-step solution
We know that a toroid is a form of solenoid which is bend in the form of a circular coil. The magnetic field due to the toroid remains inside the circular coil of the toroid and it remains in the form of the concentric circles. The magnetic field outside the toroid is zero and it varies as inversely proportional to the cube of distance of the point. i.e. (M 1 r^3 )