e&m.jpg (12862 bytes)

Back EMF in a Coil (Self and Mutual Inductance)

 

EQUIPMENT
    redball.gif (326 bytes) Inductor Device
    redball.gif (326 bytes) Switch
    redball.gif (326 bytes) Large Power Supply


NARRATIVE
       A change in potential across a coil (inductor) will cause an EMF opposing the change to be induced. This induced EMF is called back EMF.Connect the induction device to 100 VDC. When the switch is closed, an EMF is induced ti oppose the build up of magnetic fields in the coil. This back EMF causes one side of the neon bulb to light. When the switch is opened, an EMF is induced to oppose the collapse of magnetic fields in the coil. This back EMF causes the other side of the Neon tube to light thereby indicating that this EMF is in the opposite direction of the first back EMF.