An air-filled toroidal solenoid has a mean radius of 15.2 cm and a cross-sectional area of 4.98 cm2 as shown in (Figure 1) . Picture this as the toroidal core around which the windings are wrapped to form the toroidal solenoid. The current flowing through it is 11.5 A , and it is desired that the energy stored within the solenoid be at least 0.394 J .

Question

Part A:
What is the least number of turns that the winding must have?

Answer: ______ turns