电路原理Chapter 2╲tResistive Circuits.pptVIP

* * Chapter 2 Resistive Circuits ? Emphasis： 1. Series and parallel resistors 3. Source equivalent transformations 2. Resistors’ Wye-Delta transformations two-terminal network(one-port network) two-terminal passive network Equal to Req= U / I 2. 1 Series and parallel resistors Equivalent resistance P + U _ I o o o Req + U _ I o 1. Characteristics of circuits: I、 Series resistors + _ R1 Rn + _ uk i + _ u1 + _ un u Rk (a) The currents through all resistors are the same (KCL)； (b) The total voltage is equal to the sum of the voltages across the individual resistor (KVL). Req=( R1+ R2 +…+Rn) =? Rk equivalent 2. Equivalent resistance Req + _ R1 Rn + _ uk i + _ u1 + _ un u Rk u + _ Req i 3. Voltage division in series connection ? ? o + _ u R1 Rn + _ u1 + _ un i o 4. Power p1=R1i2， p2=R2i2，?， pn=Rni2 p1: p2 : ? : pn= R1 : R2 : ? :Rn p=Reqi2 = (R1+ R2+ …+Rn ) i2 =R1i2+R2i2+ ?+Rni2 =p1+ p2+?+ pn II、 Parallel resistors in R1 R2 Rk Rn i + u i1 i2 ik _ 1. Characteristics of circuits: (a) resistors in parallel have the same voltage across them (KVL)； (b) Total current is equal to the sum of currents through every resistor (KCL)。 i = i1+ i2+ …+ ik+ …+in 1/Req= 1/R1+1/R2+…+1/Rn Expressed by conductance G =1 / R : Geq=G1+G2+…+Gk+…+Gn=? Gk=? 1/Rk in R1 R2 Rk Rn i + u i1 i2 ik _ 2. Equivalent resistance Req + u _ i Req 3. Current division in parallel connection ? ? in R1 R2 Rk Rn i + u i1 i2 ik _ 4. Power p1=G1u2， p2=G2u2，?， pn=Gnu2 p1: p2 : ? : pn= G1 : G2 : ? :Gn Total power p=Gequ2 = (G1+ G2+ …+Gn ) u2 =G1u2+G2u2+ ?+Gnu2 =p1+ p2+?+ pn III、 Series and Parallel Connection distinguish between series connection and parallel connection 1. 2? 4? 3? 6? o o R Examples： 40? 30? 30? 40? 30? o o R 2. 3. Find：I1 ,I4 ,U4 + _ 2R 2R 2R 2R R R I1 I2 I3 I4 12V + _ U4 + _ U2 + _ U1 4. Find the input resistance Rab at the terminals a and b. (b ≠1) I b I a b R o o Rab + U _ 2. 2 Wye –Delta transformations (?—Y) P ° ° °