PHY2061 R. D. Field Department of Physics chp36_2.doc University of Florida Energy Stored in a Magnetic Field When an external source of EMFis connected to an inductor and current begins to flow, the induced EMF(called back EMF) will oppose the increasing current and the external EMF must do workin order to overcome this opposition. This work is stored in the magnetic fieldand can be recovered by removing the external EMF. Energy Stored in an Inductor L:The rate at which work is done by the back EMF (power) is PILIdIdtback== −ε, since ε= -LdI/dt. The power supplied by the external EMF (rate at which
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