Magnetic Fields and Energy
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The direction of the magnetic field at any point in space is the equilibrium direction of the north end of a compass placed at that point. Magnetic fields can be represented by field diagrams obtained by plotting field arrows at a series of locations. Field line diagrams are excluded from this course. Calculations for the magnetic field strength are not required at this grade level, but it is important to note that greater magnetic fields result in larger magnetic forces on magnetic objects or moving charges placed in the field. The concept of magnetic potential energy can be understood from the perspective of a magnetic field. When two attracting or repelling magnetic poles interact, the kinetic energies of both objects change but neither is acting as the energy source or the receiver. Instead, the energy is transferred into or out of the magnetic field around the system as magnetic potential energy. A single magnetic pole does not have magnetic potential energy. Only the system of attracting or repelling poles can have magnetic potential energy. When the distance between the attracting or repelling poles changes, there is a change in the magnetic potential energy of the system. When two magnetically attracting objects are moved farther apart or two magnetically repelling objects are moved close together, energy is transferred into the field as magnetic potential energy. When two magnetically attracting objects are moved closer together or two magnetically repelling objects are moved far apart, magnetic potential energy is transferred out of the field. Work is required to separate two magnetically attracting objects. If there is no change in kinetic energy and no energy is transferred out of the system, the work done on the system increases the magnetic potential energy of the system. In this course, the concepts of magnetic fields and magnetic potential energy will not be addressed mathematically.