Calculating Time Until Voltage Falls in a Circuit with Resistor and Capacitor

AI Thread Summary
To calculate the time until the voltage across a capacitor falls to a specific fraction of its initial value, the time constant (T) is determined using the formula T = cR, where c is the capacitance and R is the resistance. For a capacitor of 35 microfarads and a resistor of 120 ohms, the time constant can be calculated, and the voltage decay can be expressed using V(final) = V(initial) e^(-t/CR). Logarithms may be necessary to solve for time when setting the voltage to the desired fraction. Additionally, in a circuit with an uncharged capacitor and a bulb, the bulb will initially remain off, then gradually light up as the capacitor charges, becoming brighter over time. This behavior is consistent with the charging process of a capacitor in a series circuit.
SMUDGY
Messages
20
Reaction score
0
--------------------------------------------------------------------------------

If a charged capacitor c=35 micro farads is connected to a resistor R=120 ohms how much time will elapse until the voltage falls to 10^6/D of its original max value?

Ciruit contains a switch, resistor, emf and a capacitor in series.

Relevant equations are Time constant= T=cR and V(Final)=V(initial) e^-t/cr


I think it requires logarithms but i am not sure.

Can you please help me how to answer this.
 
Physics news on Phys.org
Another question is:

A circuit containing a switch, Vo, a capacitor and a bulb in series.

The capacior is originally uncharged. Describe the behaviour of the bulb from the instant the switch is on until a long time later.

I think there will be a delay for the bulb to emit light and then it will emit light getting slowly brighter as the capacitor is getting charged up.

Is this right?
 

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

Calculating the voltage across capacitors and resistors with switches
Replies
2
Views
726
Finding Current in Resistors & Charge of Capacitor
Replies
4
Views
2K
Circuit with resistor, switch and capacitor
2
Replies
62
Views
5K
Energy dissipated in the resistors in a 2 mesh RC circuit
Replies
1
Views
2K
RC Circuit with parallel resistor
Replies
6
Views
3K
Calculation of current in driven series RLC circuit
Replies
8
Views
2K
Calculating Voltage Decay in a Resistor-Capacitor Circuit
Replies
1
Views
2K
How to find voltage across capacitor in RLC circuit?
Replies
3
Views
1K
Finding the time for charging Voltage
Replies
9
Views
2K
Drawing a Circuit from Voltage-Time Graph
Replies
7
Views
4K

Hot Threads

Recent Insights

Back
Top