Consider the following statements about a solenoid: 1. The magnetic field strength in a solenoid depends upon the number of turns per unit length in the solenoid 2. The magnetic field strength in a solenoid depends upon the current flowing in the wire of the solenoid 3. The magnetic field strength in a solenoid depends upon the diameter of the solenoid Which of the statements given above are correct ?

The magnetic field strength inside a long solenoid is given by the formula B ≈ μ₀ n I, where μ₀ is the permeability of free space, n is the number of turns per unit length (n = N/L), and I is the current flowing through the solenoid. Statement 1 is correct as B is directly proportional to n (number of turns per unit length). Statement 2 is correct as B is directly proportional to I (current). Statement 3 is incorrect. For an ideal long solenoid, the magnetic field strength inside the solenoid (away from the ends) does not depend on its diameter. While the diameter might have minor effects in non-ideal cases (finite length solenoid, field near ends), the standard formula and theoretical treatment indicate no dependence on diameter for the uniform field inside a long solenoid.