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# Magnetic Energy

"A fact is a simple statement that everyone believes. It is innocent, unless found guilty. A hypothesis is a novel suggestion that no one wants to believe. It is guilty, until found effective"
Edward Teller

- Let's take a second look at the differential equation for the simple LR circuit

> Multiplying throughout by the current I gives
> This is now an energy conservation equation,
> Rate of thermal heating (I2R) + Rate at which energy is stored in the inductance (LI dI/dt) = Rate at which energy is supplied (εI)

- The energy stored in the inductance is associated with the magnetic field of the inductance, UB. Therefore,

> which upon integration gives
> equivalent to the electrical case of energy stored in a capacitor UE = q2/2C = (1/2)CV2.

- Exactly as in the electric field case, we can determine a general expression for the energy density (uB) stored in a magnetic field,

This girl said she recognized me from the vegetarian club, but I'd never met herbivore.

Dr. C. L. Davis
Physics Department
University of Louisville
email: c.l.davis@louisville.edu