Final answer:
Solenoid B's magnetic field is 2.7 times greater than the magnetic field of solenoid A because while it has 4 times the number of coils and 2 times the current, it is also 3 times longer, making its turns per unit length ratio and current increase only an overall factor of 2.7.
Step-by-step explanation:
The magnetic field strength inside a solenoid is given by B = μ_0nI, where μ_0 is the magnetic constant (permeability of free space), n is the number of turns per unit length, and I is the current. For solenoid B, since it has a current 2 times greater, 4 times as many coils, and is 3 times longer than solenoid A, we need to calculate how these changes affect the magnetic field.
The number of turns per unit length for solenoid B is 4 times greater than that of solenoid A, but since it's also 3 times longer, the number of turns per unit length (n) is effectively 4/3 times that of solenoid A. Multiplying this by the 2 times greater current gives us an overall factor of 8/3 times the magnetic field of solenoid A. Therefore, Solenoid B's magnetic field is 2.7 times greater than solenoid A's magnetic field.