Final answer:
When a bar magnet is placed inside a solenoid at rest, nothing happens unless the solenoid is carrying an electrical current. Once the solenoid is current-carrying, the bar magnet will align with the uniform magnetic field inside the solenoid, as described by the equation B = MonI.
Step-by-step explanation:
When a bar magnet is placed inside a solenoid at rest, initially, nothing happens because the solenoid must have an electrical current flowing through it to create a magnetic field. If the solenoid is active (current-carrying), the bar magnet will experience a force due to the interaction between the magnetic field of the bar magnet and that of the solenoid. The magnetic field strength inside an active solenoid is described by the formula B = MonI (inside a solenoid), where B is the magnetic field strength, Mo is the permeability of free space, n is the number of loops per unit length of the solenoid, and I is the current flowing through the solenoid. This field is very uniform in both direction and magnitude, except near the solenoid's ends. The bar magnet will align itself with this field if not already aligned, and if free to move, it may translate towards one end of the solenoid depending on the orientation of its poles relative to the solenoid's magnetic field.