Discharging capacitor half life

Click For Summary

Discussion Overview

The discussion centers around the concept of "discharging capacitor half life," specifically seeking clarification on its definition and mathematical representation. Participants explore both the mathematical formulation and intuitive understanding of half life in the context of capacitor discharge.

Discussion Character

  • Conceptual clarification
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant seeks confirmation on the definition of discharging capacitor half life, indicating confusion over varying descriptions.
  • Another participant provides a mathematical explanation of capacitor discharge, noting that the voltage decreases exponentially and can be expressed in terms of half life as RC/log_e(2).
  • A different participant requests a non-mathematical description of half life, leading to a clarification that it is the time required for the voltage to reduce to half of its original value.
  • Further contributions emphasize that the concept of half life applies universally, indicating that each half life period results in a voltage reduction by a factor of two.
  • One participant corrects a previous statement regarding the mathematical expression for half life, suggesting a typographical error in the representation of the equation.

Areas of Agreement / Disagreement

Participants generally agree on the intuitive understanding of half life as the time taken for the voltage to halve. However, there are differing views on the mathematical representation, with some corrections and clarifications noted throughout the discussion.

Contextual Notes

Some participants express uncertainty regarding the mathematical details and the implications of the exponential decay function, indicating a need for further clarification on the assumptions involved in the equations presented.

Googl
Messages
111
Reaction score
1
What is meant by discharging capacitor half life (the description). I seem to be getting different description, I would just like for someone to confirm it here for me please.
 
Physics news on Phys.org
If discharged through a resistor the capacitor voltage reduces exponentially via the equation

v = V_0 \, e^{-\frac{t}{RC}}

Mathematically it's easy to represent an exponential of one base in other other base.

In this case the above exponential can be re-written as

v = V_0\, 2^{-\frac{t}{\log(2) \, RC}}

where "log" is the natural logarithm.

From the above equation you can see that the "half life" is RC/\log_e(2)
 
Last edited:
Thanks Uart,

I understand that, how would you describe half life (not mathematically or through equations).

uart said:
If discharged through a resistor the capacitor voltage reduces exponentially via the equation

v = V_0 \, e^{-\frac{t}{RC}}

Mathematically it's easy to represent an exponential of one base in other other base.

In this case the above exponential can be re-written as

v = V_0\, 2^{-\frac{t}{\log(2) \, RC}}

where "log" is the natural logarithm.

From the above equation you can see that the "half life" is RC/\log_e(2)
 
Googl said:
Thanks Uart,

I understand that, how would you describe half life (not mathematically or through equations).

Well obviously, it's the time that you have to wait until the voltage is half of it's original value. That's how I'd describe it.
 
Half life of a quantity is the time it needs so that the quantity is reduced to half of its original value.

In the example of Uart, half life of the voltage is the time it gets for the voltage to reduce to the half of its starting value , that is the time it needs to go from V_0 to \frac{V_0}{2}
 
Thanks.
 
It may be worthwhile pointing out that this 'half life' applies wherever you start. So, every period of one half life decreases the voltage by a factor of two. This 'exponential' function is the only one with this property afaik. It applies in many examples of decay and growth processes (even bloody compound interest!).
 
uart said:
you can see that the "half life" is RC/\log_e(2)


Just correcting a typo above. That should of course have been RC \, \log_e(2)
 

Similar threads

  • · Replies 15 ·
Replies
15
Views
2K
Replies
152
Views
7K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 8 ·
Replies
8
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
Replies
9
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 16 ·
Replies
16
Views
2K