A giant magnet moves above a debris pile with many pieces of iron buried in it. Which statement is correct about the energy stored in the magnetic field?
A. Iron Pieces accelerate away from the magnet, and the energy stored in the system decreases.
B. Iron Pieces accelerate away from the magnet, and the energy stored in the system increases.
C. Iron pieces accelerate toward the magnet, and the energy stored in the system decreases.
D. Iron pieces accelerate toward the magnet, and the energy stored in the system increases.
C. Iron pieces accelerate toward the magnet, and the energy stored in the system decreases.
As the giant magnet moves above the debris pile, it creates a time-varying magnetic field which induces electric currents in the iron pieces buried in the debris. The induced electric currents create their own magnetic fields which oppose the motion of the magnet. According to Lenz's law, the induced magnetic field opposes the change that created it (in this case, the motion of the magnet), and as a result, the iron pieces accelerate toward the magnet, reducing the potential energy stored in the magnetic field. Therefore, the correct statement is that the iron pieces accelerate toward the magnet, and the energy stored in the system decreases.
The correct statement about the energy stored in the magnetic field in this scenario is:
C. Iron pieces accelerate toward the magnet, and the energy stored in the system decreases.
When a giant magnet moves above a debris pile with many pieces of iron buried in it, the magnetic field attracts the iron pieces, causing them to accelerate toward the magnet. As the iron pieces move closer to the magnet, the magnetic field does work on them, transferring energy to the system. This causes a decrease in the stored energy in the magnetic field.