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Key Equations

Terminal voltage of a single voltage source Vterminal=εIreqVterminal=εIreq
Equivalent resistance of a series circuit Req=R1+R2+R3++RN1+RN=i=1NRiReq=R1+R2+R3++RN1+RN=i=1NRi
Equivalent resistance of a parallel circuit Req=(1R1+1R2++1RN)−1=(i=1N1Ri)−1Req=(1R1+1R2++1RN)−1=(i=1N1Ri)−1
Junction rule Iin= Iout Iin= Iout
Loop rule V=0 V=0
Terminal voltage of N voltage sources in series Vterminal=i=1NεiIi=1Nri=i=1NεiIreqVterminal=i=1NεiIi=1Nri=i=1NεiIreq
Terminal voltage of N voltage sources in parallel Vterminal=εIi=1N(1ri)−1=εIreqVterminal=εIi=1N(1ri)−1=εIreq
Charge on a charging capacitor q(t)=Cε(1etRC)=Q(1etτ)q(t)=Cε(1etRC)=Q(1etτ)
Time constant τ=RCτ=RC
Current during charging of a capacitor I=εRetRC=IoetRCI=εRetRC=IoetRC
Charge on a discharging capacitor q(t)=Qetτq(t)=Qetτ
Current during discharging of a capacitor I(t)=QRCetτI(t)=QRCetτ
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