Induction on a Rotating Disk?

📌 CONCEPT: Electromagnetic induction on a rotating disk is a phenomenon where a current is induced in the disk due to a change in the magnetic flux through it when the rotation is reversed.

📐 RULE / FORMULA: The direction of the induced current is determined by Lenz's law, which states that the current flows in a direction such that the magnetic field it produces opposes the change in the magnetic flux.

💡 WORKED EXAMPLE: Consider a copper disk rotating at 20 rad/s in one direction. When the rotation is reversed, the magnetic flux through the disk decreases. According to Lenz's law, the induced current flows in a direction such that the magnetic field it produces opposes the decrease in magnetic flux. The direction of the induced current is opposite to the original direction of rotation.

⚠️ COMMON MISTAKE: Students often forget to consider the direction of the induced current in relation to the change in magnetic flux, leading to incorrect application of Lenz's law.