电路分享基础英文PPT (25).pdf

Mesh Current Method(1)mesh current method:a method where the circuit equation is written to analyze circuit with the mesh current as an unknown quantity.the imaginary current flowing along the mesh+s1u1R2R4R3Rs4iCan such two currents in opposite directions exist at the same time?public branchunique branchm1im2iWrite the KVL equation for the mesh column,and set the voltage drop along the direction of the mesh to be positive:Express the branch voltage as the mesh current:11 m1uRi=()22m1m2uRii=33 m2uR i=()44m2s4uRii=12s1+uuu=342=0uuu+s1u1R2R4R3Rs4i（*）（*）Substitute the（*）set of equations into the（*）one:()12m12 m2s1RRiR iu+=()2 m1234m24 s4R iRRRiR i+=mesh currentequationThe nature of the mesh current equation is KVL.finding rules()()()mmii+=12()()()mmii+=12the sum of the branch resistances of the branches directly passed by the mesh i,always positive.self-resistance:iiRthe sum of the resistance of the common branch of mesh i and mesh j,always negative with the same direction of the meshes.mutual resistance:ijRmesh voltage source:smiuthe sum of the voltage source and the equivalent voltage source passed by the mesh i.The voltage rise is positive along the direction of the mesh.+s1u1R2R4R3Rs4iPractice problem：Please write the mesh current equation in the figure.Solution:8V12V+21422m1m21+1+2+4=8ii（）(m11+2+2i）m21 i=8+12