Electric Circuits
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Updated
2009-02-26 16:15
Electric Circuits
| Equation | Meaning |
|---|---|
| Req=R1+R2 | equivalent resistance for 2 resistors in series |
| Req=[(1/R1)+(1/R2)]-1 =(R1 R2)/(R1 + R2) | equivalent resistance for 2 resistors in parallel |
| Leq=L1+L2 | equivalent inductance for 2 inductors in series |
| Leq=[(1/L1)+(1/L2)]-1 =(L1 L2)/(L1 + L2) | equivalent inductance for 2 inductors in parallel |
| Ceq=[(1/C1)+(1/C2)]-1 =(C1 C2)/(C1 + C2) | equivalent capacitance for 2 capacitors in series |
| Ceq=C1+C2 | equivalent capacitance for 2 capacitors in parallel |
| V I | Power for a current I flowing through a potential drop V |
| I2 R | Power lost for a current I flowing through a resistor R |
| V2/R | Power lost for a voltage V across a resistor R |
| (1/2) Q V | Energy stored in a capacitor |
| (1/2) Q2/C | Energy stored in a capacitor |
| (1/2) C V2 | Energy stored in a capacitor |
| (1/2) L I2 | Energy stored in an inductor |
| I R | Voltage drop across a resistor |
| Q/C | Voltage drop across a capacitor |
| L dI/dt | Voltage drop across an inductor |
| dQ/dt | Current flowing through a capacitor |
| C V | Charge stored on a capacitor |
| 0 | Total charge on an isolated piece of a circuit |
| 0 | Total current entering - Total current leaving a point in a circuit |
| 0 | Total voltage change for a loop in a circuit |
| 0 | Electric Field inside a conductor |
| (ρ L)/A | Resistance of a piece of wire |
| ∞ | Resistance across a break in a circuit |
AC Circuits
| Equation | Meaning |
|---|---|
| i | sqrt(-1) |
| 1/i | -i |
| 1/(ωC) | reactance of a capacitor |
| ωL | reactance of an inductor |
| 1/(iωC) | impedance of a capacitor |
| iωL | impedance of an inductor |
| R | impedance of a resistor |
| Vrms | root mean squared voltage |
| Vo/sqrt(2) | Vrms when V(t)=Vosin(ωt) |
| Irms | root mean squared current |
| Io/sqrt(2) | Irms when I(t)=Iosin(ωt-φ) |
| Irms2 R = (1/2) Io2 R | Average power dissipated by a resistor in an AC circuit |
| Vrms2/R = (1/2) Vo2/R | Average power dissipated by a resistor in an AC circuit |
| Vrms Irms = (1/2) Vo Io | Average power in an AC circuit |
