[物理]CircuitAnalysis电路分析基础英文版实用.pdf

EIE209 Basic Electronics Basic circuit analysis Prof. C.K. Tse: Basic Circuit Analysis 1 Fundamental quantities ® Voltage — potential difference bet. 2 points ® “across” quantity ® analogous to ‘pressure’ between two points ® Current — flow of charge through a material ® “through” quantity ® analogous to fluid flowing along a pipe Prof. C.K. Tse: Basic Circuit Analysis 2 Units of measurement n Voltage: volt (V) n Current : ampere (A) n NOT Volt, Ampere!! Prof. C.K. Tse: Basic Circuit Analysis 3 Power and energy Work done in moving a charge dq from A to B having a potential difference of V is W = V dq dq A B Power is work done per unit time, i.e., Prof. C.K. Tse: Basic Circuit Analysis 4 Direction and polarity n Current direction indicates the direction of flow of positive charge n Voltage polarity indicates the relative potential between 2 points: + assigned to a higher potential point; and – assigned to a lower potential point. n NOTE: Direction and polarity are arbitrarily assigned on circuit diagrams. Actual direction and polarity will be governed by the sign of the value. Prof. C.K. Tse: Basic Circuit Analysis 5 Independent sources n Voltage sources Independent — stubborn! never change! n Current source