time constant

physics

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July 14, 2026

Quick Summary

The term "time constant" in physics refers to the time it takes for a system to reach approximately 63.2% of its final value when subjected to a steady force. This concept applies to both electrical circuits and decaying populations.

In an electrical circuit, the time constant is the ratio of inductance to resistance, or the product of resistance and capacitance. It indicates how quickly a current reaches its maximum strength or how long it takes for a capacitor to discharge.1

For radioactive decay, the "decay constant" (λ) relates the population size of radioactive atoms to the rate of decrease. The equation dN/dt = -λN describes this relationship, where N is the population size at time t. The population decays exponentially, and the half-life (the time for half the atoms to decay) is related to the decay constant by T_1/2 = 0.693/λ.2

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…of configuration has an associated time constant given by the product of the resistance and capacitance values (RC). For simplicity, it will be assumed that this time constant is long compared with the charge collection time in the detector but small relative to the average time between interactions of individual…
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…of configuration has an associated time constant given by the product of the resistance and capacitance values (RC). For simplicity, it will be assumed that this time constant is long compared with the charge collection time in the detector but small relative to the average time between interactions of individual…
Read More