Capacitors - Charging/Discharging
By DarthVader
Date: 2024-10-24
Topic: 208 see comments
Post views: 33
Time constant
The time constant (τ) for a resistor capacitor pair is:
τ = RC
where:
R = Resistance (Ω)
C = Capacitance (F)
Charging
A capacitor reaches 99% of full charge in 4.6 × τ
Voltage during charging:
V = Vs(1 − e−t/RC)
Voltage during discharging:
V = Vs(e−t/RC)
Max charge:
Q = CV
where:
Q = Charge in coulombs (C)
C = Capacitance (F)
V = Voltage (V)
Total capacitance:
C = (εA) / (d) or C = (ε0εrA) / (d)
where:
C = Capacitance (F)
d = Distance between plates (m)
A = Area of the conducting plates (m2)
ε = Permittivity of the dielectric between plates
ε0 = Permittivity of free space ≈ 8.85 pF m-1
εr = Relative permittivity of the dielectric - (no units)
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