A toroid has a core (non ferromagnetic material) of inner radius `25cm` and outer radius `26cm` around which 3500 turns of wire are wound. If the current in the wire is `11A`, what is the magnetic field (a) outside the toroid (b) inside the core of the toroid (c) in the empty space surrounded by the toroid?

Explanation

Inner radius of the toroid, `r_(1) = 25 cm = 0.25m`
Outer radius of the toroid, `r_(2) = 26 cm = 0.26m`
Number of turns on the coil, `N = 3500`
Current in the coil, `I = 11A`
(a) Magnetic field outside a toroid is zero. It is non-zero only inside the core of a toroid.
(b) Magnetic field inside the core of a toroid is given by the relation,
`B = (mu_(0)NI)/(l)`
Where,
`mu_(0) =` Permeability of free space `= 4pi xx 10^(-7)TmA^(-1)`
`l =` length of toroid
`=2pi [(r_(1)+r_(2))/(2)]`
`= pi (0.25 +0.26)`
`= 0.51pi`
`:. B = (4pi xx 10^(-7) xx 3500 xx 11)/(0.51 pi)`
`~~ 3.0 xx 10^(-2)T`
(c) Magnetic field in the empty space surrounded by the toroid is zero.