Final answer:
To calculate the magnetic field at the center of a toroid solenoid, use the formula involving the permeability of free space, the number of turns, current, and the toroid's mean radius. The exact magnetic field can be determined once the mean radius is known.
Step-by-step explanation:
The student's question pertains to the calculation of the magnetic field at the center of a toroidal solenoid. A toroidal solenoid is essentially a solenoid bent into a circular shape, creating a donut-like form. The number of turns per length and the current through the solenoid are critical to determine the magnetic field.
To find the magnetic field inside a toroid, the formula B = (mu_0 * N * I) / (2 * pi * r) is used, where mu_0 is the permeability of free space, N is the number of turns, I is the current, and r is the mean radius of the toroid.
For the given toroid with 21 turns per centimeter and a current of 43 mA (0.043 A), we would need to know the mean radius to calculate the exact magnetic field. However, for each turn of the toroid, you can expect a similar calculation approach using the aforementioned formula, multiplying the number of turns per unit length by the length of the toroid to find N.