\[\tau=R_mC_m\]
Variables
taumembrane time constant (s)
Rmmembrane resistance (Ω)
Cmmembrane capacitance (F)
Description
What is this formula?
This formula calculates the RC time constant of a biological membrane modeled as an electrical resistor-capacitor circuit. The time constant determines how quickly the membrane potential changes in response to electrical stimulation.
When to use it
Use this formula in electrophysiology, neuroscience, or cellular biophysics when analyzing membrane charging and signal propagation.
Example
A neuron membrane has:
Rm=1.5×10^7 Ω
Cm=1.2×10^-9 F
Formula:
tau=Rm*Cm
Substitution:
tau=(1.5×10^7)*(1.2×10^-9)
Result:
tau=0.018 s
The membrane time constant is 18 ms.
Applications
- Neuron signal modeling
- Action potential analysis
- Cellular electrophysiology
- Bioelectric circuit models
- Membrane dynamics studies