Case: Read the passage and answer the below questions

The toroid is a hollow circular ring on which a large number of turns of wire are closely wound. It can be viewed as a solenoid that has been bent into a circular shape to close on itself. The magnetic field vanishes in the open space inside and outside the toroid. The magnetic field inside the toroid is constant in magnitude and is given by B = µ₀ n I, where n is the number of turns per unit length and I is the current flowing in the toroid, and µ0 is the absolute permeability of the free space.

The magnetic field inside a toroid of radius R is B. If the current through it is doubled and its radius is also doubled keeping the number of turns per unit length the same, magnetic field produced by it will be;

2B

B = µ₀ n I

Current and radius is doubled . Then new magnetic field B'

B' = µ₀ n (2i)

    = 2µ₀ n I = 2B