Final answer:
The magnetic field at the center of each turn of a toroid can be calculated using a specific formula from Ampere's Law, but the central radius of the toroid is needed to provide a numerical answer. The given current of 43 mA (0.043 A) and the number of turns per centimeter from the solenoid will be used once the radius is known.
Step-by-step explanation:
To find the magnetic field at the center of each turn of the toroid shaped from the solenoid, you can use Ampere's Law. Since a toroid is essentially a solenoid bent into a circle, it keeps most properties of a solenoid. Given that the original solenoid has 21 turns per centimeter, when twisted into a toroid, this winding density remains the same. To calculate the magnetic field in the toroid, the formula from the Biot-Savart law or Ampere's law for a toroid can be used:
B = (mu_0 * N * I) / (2 * pi * r)
where B is the magnetic field, mu_0 is the permeability of free space (4*pi x 10^-7 T*m/A), N is the total number of turns, I is the current in amperes, and r is the radius of the toroid. To provide a specific answer, though, we need the central radius of the toroid. Without the radius, it's not possible to determine the magnetic field.
However, assuming the radius is known, just multiply the number of turns per length by the circumference to get number of turns, and then apply the formula to find B. The current given is 43 mA, which is 0.043 A for your calculations. Make sure to express your final answer with appropriate SI units, Tesla (T).