The Class Notes

4 jan 2010

$Limit\ A\ \to \infty :$

$X_{0}\ ={\frac {1}{\beta }}X_{s}\ \Rightarrow V_{0}={\frac {R_{1}+R_{2}}{R_{1}}}V_{in}$

$X_{i}\ =0$

Picture drawn by Kirk Betz based on drawing by Dr. Frohnes, lecture Jan. 4, 2010

$V_{in}\ =V_{0}({\frac {R_{1}}{R_{1}+R_{2}}})$.

$V_{0}\ ={\frac {1}{({\frac {R_{1}}{R_{1}+R_{2}}})}}V_{in}$

Magnetic Circuits

jan 6 2010

${\vec {F}}\ =q{\vec {v}}\times {\vec {B}}$

$d{\vec {F}}\ =Id{\vec {\ell }}\times {\vec {B}}$

${\mathcal {F}}=H\ell _{1}+H\ell _{2}$

$V\ =R_{1}I+R_{2}I$

Picture drawn by Kirk Betz based on drawing by Dr. Frohnes, lecture Jan. 6, 2010

Magnetic Equations

$\int {\vec {H}}d{\vec {\ell }}={\mathcal {F}}$

$\oint {\vec {H}}d{\vec {\ell }}=Ni=\sum _{n}H\ell +Ni=0$

$\oint {\vec {B}}d{\vec {s}}=0$

$\int {\vec {B}}d{\vec {s}}=\phi \thickapprox BA_{rea}\ Magnetic\ Flux$

${\mathcal {R}}\equiv Reluctance\ {\frac {\mathcal {F}}{\phi }}={\frac {Ni}{\phi }}$

${\vec {B}}=\mu {\vec {H}}\ Assumes\ Linearity$

${\mathcal {R}}{\frac {\ell }{\mu A}}$

Picture drawn by Kirk Betz based on drawing by Dr. Frohnes, lecture Jan. 6, 2010

Pictures drawn by Kirk Betz based on drawing by Dr. Frohnes, lecture Jan. 6, 2010

Magnetic Circuits Examples

What about chancing currents, etc.?

Picture drawn by Kirk Betz based on drawing by Dr. Frohnes, lecture Jan. 8, 2010

$\oint {\vec {H}}d{\vec {\ell }}=Ni$

Case i)

$\mu =10^{4}\mu _{0}\ in\ the\ core$ Something about this part doesn't seem right.

$Find\ {\vec {B}}\ in\ the\ gap.$

Graph and picture 6

$H\ell \ =NI$, $\ I\ \varpropto H$

$NI\ ={\mathcal {F}}\backsim V$

${\mathcal {R}}={\frac {\ell }{\mu A}}\backsim R={\frac {l}{\sigma A}}$

$\phi \ =BA\backsim I=JA$

$R_{c}={\frac {\ell _{1}}{\mu A}}$

$R_{g}={\frac {g}{\mu _{0}({\sqrt {A}}+g)^{2}}}$