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

Inner radius of the toroid, r1 = 25 cm = 0.25 m

Outer radius of the toroid, r2 = 26 cm = 0.26 m

Number of turns on the coil, N = 3500

Current in the coil, I = 11 A

(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,

image027 NCERT Solutions class-12 physics Moving Charges and Magnetism

Where,

image004 NCERT Solutions class-12 physics Moving Charges and Magnetism = Permeability of free space = image014 NCERT Solutions class-12 physics Moving Charges and Magnetism

l = length of toroid

image090 NCERT Solutions class-12 physics Moving Charges and Magnetism

image091 NCERT Solutions class-12 physics Moving Charges and Magnetism

image092 NCERT Solutions class-12 physics Moving Charges and Magnetism

image093 NCERT Solutions class-12 physics Moving Charges and Magnetism

image094 NCERT Solutions class-12 physics Moving Charges and Magnetism

(c) Magnetic field in the empty space surrounded by the toroid is zero.

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