The Class Notes

Notes for reviewer Be sure all 'l' have been replaced with $\ell$

4 jan 2010

$$\begin{gathered} Limit \\ A \\ \to \mathrm{\infty }: \end{gathered}$$

$$\begin{gathered} X_0 \\ =\frac{1}{\beta }{X}_s \\ \Rightarrow V_0=\frac{R_1+R_2}{R_1}{V}_{in} \end{gathered}$$

$$\begin{gathered} X_i \\ =0 \end{gathered}$$

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

$$\begin{gathered} V_{in} \\ =V_0(\frac{R_1}{R_1+R_2}) \end{gathered}$$.

$$\begin{gathered} V_0 \\ =\frac{1}{(\frac{R_1}{R_1+R_2})}{V}_{in} \end{gathered}$$

Magnetic Circuits

jan 6 2010

$$\begin{gathered} \overrightarrow{F} \\ =q\overrightarrow{v}\times \overrightarrow{B} \end{gathered}$$

$$\begin{gathered} d\overrightarrow{F} \\ =Id\overrightarrow{\ell }\times \overrightarrow{B} \end{gathered}$$

${ℱ}=H{\ell }_1+H{\ell }_2$

$$\begin{gathered} V \\ =R_{1}I+R_{2}I \end{gathered}$$

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

Magnetic Equations

$\int \overrightarrow{H}d\overrightarrow{\ell }={ℱ}$

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

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

$$\begin{gathered} \int \overrightarrow{B}d\overrightarrow{s}=\varphi \approx B{A}_{rea} \\ Magnetic \\ Flux \end{gathered}$$

$$\begin{gathered} {ℛ}\equiv Reluctance \\ \frac{{ℱ}}{\varphi }=\frac{Ni}{\varphi } \end{gathered}$$

$$\begin{gathered} \overrightarrow{B}=\mu \overrightarrow{H} \\ Assumes \\ Linearity \end{gathered}$$

${ℛ}\frac{\ell }{\mu A}$

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

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

Case i)

$$\begin{gathered} \mu =10^4{\mu }_0 \\ in \\ the \\ core \end{gathered}$$ Something about this part doesn't seem right.

$$\begin{gathered} Find \\ \overrightarrow{B} \\ in \\ the \\ gap. \end{gathered}$$

Graph and picture 6

$$\begin{gathered} H\ell \\ =NI \end{gathered}$$, $$\begin{gathered} I \\ \propto H \end{gathered}$$

$$\begin{gathered} NI \\ ={ℱ}\backsim V \end{gathered}$$

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

$$\begin{gathered} \varphi \\ =BA\backsim I=JA \end{gathered}$$

$R_c=\frac{{\ell }_1}{\mu A}$

$R_g=\frac{g}{{\mu }_0(\sqrt{A}+g{)}^2}$

$$\begin{gathered} \varphi \\ =B(\sqrt{A}+g{)}^2=\frac{NI}{R_g+R_c} \end{gathered}$$

$B_g\frac{NI}{(R_g+R_c)(\sqrt{A}+g{)}^2}$