Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

How does the radius of a solenoid affect its magnetic field strength?

1. It has no effect on the field strength

2. A larger radius increases the field strength

3. A smaller radius increases the field strength

4. It only affects the direction of the field

The correct answer is: A larger radius increases the field strength

The relationship between the radius of a solenoid and its magnetic field strength can be understood through the principles of electromagnetism. The magnetic field inside a long solenoid is defined primarily by the number of turns of wire per unit length and the current flowing through the wire, according to the formula \(B = \mu_0 \cdot \frac{N}{L} \cdot I\), where \(B\) is the magnetic field strength, \(\mu_0\) is the permeability of free space, \(N\) is the number of turns, \(L\) is the length of the solenoid, and \(I\) is the current. When considering the radius of the solenoid, while the formula does not explicitly include the radius, the geometry affects the uniformity and distribution of the magnetic field. A larger radius tends to distribute the magnetic lines of force over a larger area, leading to a more spread-out field that can sometimes give the impression that the field strength decreases on a per unit area basis at any particular point if viewed superficially. However, the effective magnetic field strength inside the solenoid tends to be more uniform and can be perceived as being stronger because the total area affected by the magnetic field