Direct current circuts

Direct Current Circuts

• Units and Variables

  • ℰ- electromotive force, in volts
  • r - internal resistance, in ohms
  • I - current, in amperes
  • R - load resistance, in ohms
• $\mathrm{\Delta V}=ℰ-Ir$
• $ℰ=I\left(R+r\right)$

• Parallel Combination of Resistors

  • $I_{\mathrm{equivalent}}=I_1+I_2+\dots$
  • $\frac{1}{R_{\mathrm{equivalent}}}=\frac{1}{R_1}+\frac{1}{R_2}+\dots$

• Series Combination of Resistors

  • $I_1=I_2=I_3=\dots$
  • $R_{\mathrm{equivalent}}=R_1+R_2+\dots$

• Kirchoff's Rules

  • Junction Rule

    • $\Sigma I_{\mathrm{in}}=\Sigma I_{\mathrm{out}}$

  • Loop Rule

    • $\underset{\mathrm{closed\; loop}}{\Sigma }\mathrm{\Delta V}=0$