[기초회로이론] Chap 01 - Electric Circuit Variables

📣 Disclaimer : Dorf’s Introduction to Electric Circuits Global Ed. 를 바탕으로 작성된 정리입니다

1.2 Electric Circuits and Current

• Mostly considers a general ‘two-terminal electrical element’

\[i={dq \over dt}\]

• DC (direct current) : current of constant magnitude (also expresses terms that are invarient over time. eg : DC voltage)
• AC (alternating current) : Current that changes its sign (eg : sinusodial current)

1.3 Systems of Units

• SI base units : Length($m$), Mass($kg$), Time($s$), Electric current($A$), Thermodynamic temperature($K$)
• Derived units : Frequency(Hz, $s^{-1}$), Work/Energy($J$, $N\cdot m$), Power($W$, $J/s$), Electrical Charge($C$, $A\cdot s$), Electric potential($V$, $W/A$), Electric resistance($\Omega$, $V/A$), Electrical conductance($S$(siemens), $A/V$), Electric capacitance($F$, $C/V$)
• SI prefixes : tera/giga/mega/kilo/ o / milli / micro / nano / pico … ($\times 10^3$)

1.4 Voltage

• Direction of voltage is given by its polarities (+, -) Plus to minus.
• $v_{+-}$, recall the battery

\[v={dw\over dq}\]

1.5 Power and Energy

\[p={dw\over dt}=vi\]

• if the direction of current and direction of (+ to - terminal which we assigned previously), is the power received by the element.
• Conversely, it is the power supplied by the element