串联时：电流I = I1 =I2=……;电压U= U1 + U2 +……电阻R= R1=R2 =……
并联时：电流I = I1+ I2+……;电压U =U1 =U2 =……电阻1/ R = 1/ R1 + 1/ R2 +…
欧姆定律：I = U/ R
电功：W =Pt = U· I ·t
电功率：P = W/ t = U I =U²/ R = I² R
电热：Q = I² R t