How do I calculate the time it takes to discharge a capacitor?

  • Thread starter Thread starter puhdanks
  • Start date Start date
  • Tags Tags
    Capacitor
AI Thread Summary
To calculate the time it takes to discharge a capacitor, the key equation is q = q₀e^(-t/RC), where q is the charge at time t, q₀ is the initial charge, R is resistance, and C is capacitance. To find the time t for a specific percentage drop in charge, rearrange the equation to isolate t. This involves taking the natural logarithm of both sides and solving for t, resulting in t = -RC * ln(q/q₀). Knowing the values of R and C will allow for the calculation of discharge time. Understanding this process is essential for preparing for the test question.
puhdanks
Messages
10
Reaction score
0
I have a test coming up and i know what some question will be on. One question is about the time it takes to discharge a capacitor from "full" to a given point or percent of initial charge. How would i go about doing this.



I know the it has to do with the time constant RC and the equation of discharging a capacitor i just don't know how i would find the time it takes.



The Attempt at a Solution

 
Physics news on Phys.org
You said you know the equation for discharging a capacitor, so what is that equation? Is it not an equation for the TIME to discharge a capacitor? If not, what is it?
 
well i guess i should have said i think i need to use it and its [q=q(naught)e^(-t/RC)]
 
does it just become [(percent droped)=e^(t/rc) i will probably be given r and c
 
Yes, you have right idea, so now how do you solve that for t ?
 

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 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'

Thread 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'

Figure 1 Overall Structure Diagram Figure 2: Top view of the piston when it is cylindrical A circular opening is created at a height of 5 meters above the water surface. Inside this opening is a sleeve-type piston with a cross-sectional area of 1 square meter. The piston is pulled to the right at a constant speed. The pulling force is（Figure 2）： F = ρshg = 1000 × 1 × 5 × 10 = 50,000 N. Figure 3: Modifying the structure to incorporate a fixed internal piston When I modify the piston...
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

Why Do Capacitors Behave Differently in Series and Parallel Configurations?
Replies
20
Views
2K
Calculating low frequency cutoff for this R-C microphone circuit
Replies
43
Views
3K
Capacitor Questions Charging and Discharging
Replies
4
Views
3K
A Capacitor with initial charge
Replies
3
Views
3K
Why can we model spherical capacitor with two dielectrics as two capacitors in series?
Replies
4
Views
2K
Finding the time for charging Voltage
Replies
9
Views
2K
Maximum current through a capacitor
Replies
1
Views
3K
How to calculate R1 and R2 in this RC circuit
Replies
3
Views
3K
Ranking charge stored on three capacitors by a battery
Replies
6
Views
3K
Determining Inductance L in an LC Circuit
Replies
5
Views
2K

Hot Threads

Recent Insights

Back
Top