Given, inner radius, r1=20‌cm=0.2m Outer radius, r2=25cm=0.25m Number of turns, N=800 Current in the toroid, I=12A Magnetic field due to N circular rings ( coroid), B=
µ.NI
2Ï€r
Magnetic field is maximum at rmin=0.2m Bmax=
4π×10−7×800×12
2Ï€(0.2)
=9.6×10−3T =9.6‌mT Magnetic field is minimum at rmax=0.25m Bmin=
4π×10−1×800×12
2π×(0.25)
=7.68×10−3T =7.68‌mT So, the maximum value of magnetic field within the toroid is 9.6‌mT and minimum value of magnetic field within the toroid is 7.68‌mT.