Energy in a Coupled Circuit
Wednesday, 20 March 2019
5:13 PM
Consider a magnetically coupled circuit pair.
As (some current, the power becomes 
The energy stored is Joules
Keeping constant at , increasing from zero to , the mutual voltage induced in coil one
is , while the mutual voltage induced in
coil two is zero, since does not change
Power is now 
The energy stored is 
Total Energy - 
Since and are arbitrary values, they can be replaced by and -
which gives the instantaneous values
---------
Limit of M
Total energy stored must be greater than zero
The extent to which the mutual inductance approaches the upper limit is specified by the
coefficient
of coupling 
Where …
or … 
The coupling coefficient is the fraction of the total flux [………………………………..]
The coupling coefficient depends on:
- Closeness of the coils
- Magnetic properties of the coil material
- Magnetic properties of the core
- Coil orientation
- Coil winding arrangement