Physics 201- Introduction to Electricity & Magnetism
December 2- Induced Magnetic Fields and Maxwell's Equations






  Induced electric fields/ emfs/ currents

A 120 turn coil, of radius 1.8cm and resistance 5.3W is placed outside a long solenoid with 220 turns/ cm and diameter 3.2cm.  The initial current in the solenoid is 1.5A and this is reduced to zero and then raised 1.5A in the opposite direction (alternating current) over a period of 50ms.  Let's say that the solenoid's current is given by the following equation:

What is the current in the coil?

This essentially is a transformer.  By pairing together two coils with different number of turns it is possible to step up or down the current & voltage.


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Jeff Phillips
Loyola Marymount University
Fall 2002