  # Electrical Circuits (AC)

 Q:     A particular experiment requires a beam of light of very stable intensity.  Why would AC voltage be unacceptable for powering the light? A:    The light emitted by a light bulb is due to heating of the bulb's filament when electric current passes through it.  In order to achieve light emission of high stability.  A constant current is needed.  This cannot be provided by an AC current, since the AC current varies in time.

## References

### Equations

Oscillating LC circuit energy transfers and (U = UE + UB)

Differential equation of LC oscillation (with no resistance)
 Differential Equation Solution Charge amplitude (maximum charge on capacitor) Q Angular frequency ( ) of the oscillations Current (i) of the system Damped oscillations
 Differential Equation Solution for For small R, '  and the maximum energy of the electric field in the capacitor is External alternating emf causing a series RLC circuit to be set into forced oscillations at a driving angular frequency ( d) Current driven in the RLC circuit by the emf Series RLC circuit current amplitude Series RLC circuit phase constant Series RLC circuit impedance (Z) Series RLC circuit current amplitude (rewritten) I = m/Z
Average power (Pav) "rms" stands for root-mean-square.   "rms" quantities are related to maximum quantities by xrms = x / So Irms = I / ,   Vrms = V / ,  and rms = / , and

Transformation of voltage Transformation of currents Equivalent resistance of the secondary circuit in a transformer as seen by the generator # List of Topics

 Measurements Electric Potential Magnetism Electrical Circuits (AC) Optical Instruments: Mirrors and Lenses Electrostatics Capacitance Sources of Magnetic Fields Maxwell's Equations Interference Electric Fields Current and Resistance Magnetism in Matter Electromagnetic Waves Diffraction Electric Flux Electrical Circuits (DC) Electromagnetic Induction Interaction of Radiation with Matter: Reflection, Refraction, Polarization  ครั้งที่

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