If a length of wire carrying a current is bent to form a loop, where will the lines of force enter?

When a length of wire carrying an electric current is bent to form a loop, the magnetic field produced by the current in the wire creates lines of magnetic force, often referred to as magnetic field lines. According to the right-hand rule, if you curl your fingers in the direction of current flow through the wire loop, your thumb points in the direction of the magnetic field lines inside the loop.

In this configuration, the magnetic field lines emerge from one side of the loop and enter from the opposite side. This means that if the field lines are exiting at the top of the loop, they will re-enter at the bottom, demonstrating that they traverse from one side of the loop to the other. This understanding is crucial in comprehending how magnetic fields interact with electrical currents, particularly in applications involving inductors or transformers.

This aligns with classical electromagnetism, where the behavior of magnetic fields is determined by the current configuration, and the concept reinforces the notion that magnetic field lines are continuous and must form closed loops. Hence, the correct identification of the entry point of the magnetic field lines is from the opposite side of the loop.