PhysicsChapter 6: Alternating Current
Rl and RC Series Circuits
An **RL circuit** contains resistance and inductance, while an RC circuit
Definition
An RL circuit contains resistance and inductance, while an RC circuit contains resistance and capacitance. Their AC behaviour is determined by resistance, reactance and phase difference.
Series RL Circuit
For resistor `R` and inductor `L`: **Z=√(R²+XL²) where: XL=ωL RMS current: I=VZ Phase angle: tanφ=XfracLR Current lags** the supply voltage.
Series RC Circuit
For resistor `R` and capacitor `C`: **Z=√(R²+XC²) where: XC=1ωC Phase magnitude: tan|φ|=XfracCR Current leads** the supply voltage.
Why Voltages Are Not Added Arithmetically
`V_R` and reactive voltage are out of phase. Therefore phasor/vector-like addition is required rather than simply adding their magnitudes.
Formula / Key Relation
RL: **Z=√(R²+XL²) tanφ=XfracLR RC: Z=√(R²+XC²) tan|φ|=XfracCR**
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Rl and RC Series Circuits
Sticky Notes · Quick Revision
RL:
- `Z=√(R²+XL²)`
- I lags
- RC:
- `Z=√(R²+XC²)`
- I leads
60-second revision
- Impedance combines resistance with reactance and determines AC current.
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