Final answer:
The greatest magnetic field strength is found in the loop with the smallest radius or in a solenoid with more turns per unit length and higher current. The least would be in the loop with the largest radius, and the medium would be dependent on other factors, such as distances from the measurement point and the magnitude of the current in the case of multiple loops.
Step-by-step explanation:
When discussing which loop has the greatest, medium, and least magnitude of magnetic field strength, various factors such as the number of turns in the loop, the current flowing through the loop, and the distance from the loop center must be considered.
For a circular loop with a steady current, the magnetic field strength is directly proportional to the current and inversely proportional to the radius of the loop. Therefore, among loops with the same current, the one with the smallest radius will have the greatest magnetic field strength at its center, and the one with the largest radius will have the least.
In the case of a solenoid, the magnetic field strength inside is proportional to the number of turns per unit length (N) and the current (I). A solenoid with more turns per unit length and higher current will have a greater magnetic field strength.
Lastly, when considering multiple loops like in Example 12.5, the net magnetic field strength at a point P depends on the contribution of each loop, which is influenced by their respective radii and distances from point P.