EMEC - Greg

Definitions

Symbol	Units	Name
${\overrightarrow {E}}$	${\frac {V}{M}}$	Electric Field Intensity
${\overrightarrow {D}}$	${\frac {C}{M^{2}}}$	Electric Flux Density
${\overrightarrow {H}}$	${\frac {A}{M}}$	Magnetic Field Intensity
${\overrightarrow {B}}$	$T={\frac {W}{M^{2}}}$	Magnetic Flux Density

Analogies between Electric & Magnetic Circuits

Electric	Magnetic
$V=\int {\overrightarrow {E}}\cdot {\overrightarrow {dl}}$	${\overrightarrow {F}}=\int {\overrightarrow {H}}\cdot {\overrightarrow {dl}}$
$\sum _{n}V_{n}=0=\oint {\overrightarrow {E}}\cdot {\overrightarrow {dl}}$ Kirchoff's voltage law	$\oint {\overrightarrow {H}}\cdot {\overrightarrow {dl}}=N\cdot i=\sum _{n}H\cdot l+N\cdot i=0$
$\sum _{n}I_{n}=0=\oint _{S}{\overrightarrow {J}}\cdot {\overrightarrow {dS}}$ Kirchoff's current law	$\oint {\overrightarrow {B}}\cdot {\overrightarrow {dS}}=0$ The B-field has to go around in a loop
$\oint {\overrightarrow {J}}\cdot {\overrightarrow {dS}}=I$	$\int {\overrightarrow {B}}\cdot {\overrightarrow {dS}}=\overbrace {\Phi } ^{phi}$ Magnetic flux
$R={\frac {V}{I}}$	$\overbrace {R} ^{reluctance}={\frac {F}{\Phi }}={\frac {N\cdot i}{\Phi }}$
$I={\frac {V}{R}}=G\cdot V$ or ${\overrightarrow {J}}=\sigma \cdot {\overrightarrow {E}}$	${\overrightarrow {B}}=\mu \cdot H$ assumed linearity (though it's not always the case - think hysteresis loop

Parenthesizing big expressions, brackets, bars

Feature	Syntax	How it looks rendered
Bad	( \frac{1}{2} )	$({\frac {1}{2}})$
Good	\left ( \frac{1}{2} \right )	$\left({\frac {1}{2}}\right)$