How Do You Calculate Time in a Charging Capacitor Equation?

AI Thread Summary
To calculate the time for a charging capacitor to reach a specific voltage, the equation V = V0*[1 - e^(-t/RC)] is used. The user attempted to rearrange it to t = -RC*ln(V/V0), but encountered issues with the logarithmic steps. Feedback indicated a misunderstanding of logarithmic properties, specifically regarding ln(1+x) and ln(1-x). The discussion suggests that the lecturer may prefer an intuitive approach rather than a strict mathematical solution. Ultimately, the user decided to postpone the problem for now, appreciating the guidance received.
MidlandSoul
Messages
2
Reaction score
0

Homework Statement


Solving the equation: V = V0*[1 - e^(-t/RC)]

Homework Equations


Need to solve this equation for time to calculate the time at which a charging capacitor achieves a certain voltage across it's plates.

The Attempt at a Solution


I solve it as: t = -RC*ln(V/V0) but this doesn't seem to work. Help!
 
Physics news on Phys.org
it looks like you might have done a step like this: ln(1+x) = ln(x) But this is not true.

Edit: Oh, welcome to physicsforums by the way!
 
Show your work step by step & we'll show you where you went wrong.
 
BruceW said:
it looks like you might have done a step like this: ln(1+x) = ln(x)
Or rather, ln(1-x) = ln(x)
 
Thanks guys. I think our lecturer intends for us to sort of 'have a guess' by inspection and using time constant ratios than actually solve this, so I can leave it for another day, phew!
Thank you for the feedback nonetheless.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Final Charge of a Capacitor in a Circuit with Capacitors and Resistors
Replies
9
Views
2K
Irodov 1.23 confusion: Calculate distance traveled and time elapsed for this decelerating particle
Replies
2
Views
824
How to find voltage across capacitor in RLC circuit?
Replies
3
Views
1K
Finding charge on a capacitor given potential difference across two points
Replies
4
Views
2K
Capacitor Questions Charging and Discharging
Replies
4
Views
3K
TIme needed for a capacitor to reach a fraction of its final charge
Replies
2
Views
2K
Understanding Capacitor Equations and Time Constants
Replies
11
Views
2K
Finding the time for charging Voltage
Replies
9
Views
2K
What does "Fully Charged Capacitor" mean?
Replies
6
Views
3K
How Does a Capacitor Charge to Negative Voltage in an RC Circuit?
Replies
20
Views
4K

Hot Threads

Recent Insights

Back
Top