Page 284: Current flowing through a coil induces a magnetic field. What will cause the coil to spin?

When an electric current flows through a coil, it generates a magnetic field around the coil due to the movement of charges (as described by Ampère's Law). For the coil to spin, there must be an interaction between this induced magnetic field and an external magnetic field. Here's how it works: 1. **Magnetic Interaction:** The induced magnetic field of the coil interacts with an existing external magnetic field (such as that from a permanent magnet or another coil). 2. **Lorentz Force and Torque:** This interaction results in forces on different parts of the coil. According to the Lorentz force law, these forces create a torque on the coil because opposite sides of the coil experience forces in opposite directions. 3. **Rotation:** The torque causes the coil to rotate. As the coil spins, it continuously adjusts to maintain alignment with the external magnetic field, leading to ongoing rotation as long as current flows through the coil. This principle is fundamental in the operation of electric motors, where coils of wire rotate within magnetic fields to generate mechanical motion. **In summary:** A current-carrying coil experiences torque from its magnetic field interacting with an external magnetic field, and this torque causes the coil to spin.