Find Capacitance from Graph of a Capacitor

In summary, the conversation discussed creating a graph of a capacitor's potential over time, which shows an exponential curve. The formula for a discharging capacitor is V(t) = V_0*e^(-t/tau), and there are multiple ways to find tau from the graph. To find resistance, you would need to know the initial current in the circuit, I0.
  • #1
UrbanXrisis
1,196
1
My class did a graph of a capacitor. Potential v. time. It showed an exponential curve. How do I find the capacitance by using that graph?

C=t/R but how do I find the resistance?

What must be present to produce a voltage across a capacitor or a resistor?
 
Physics news on Phys.org
  • #2
Did you also learn what the formula for that graph is?

For a discharging capacitor it is:

[tex]V(t) = V_0e^{-\frac{t}{\tau }}[/tex]

There are, if I remember correctly, about four ways to find [itex]\tau [/itex] from that graph, but the easiest method is to pick any point on the graph, and subtitute the values of t and V(t) in the equation above, and you can find [itex]\tau [/itex], from which you can find C providing you know R.

"What must be present to produce a voltage across a capacitor or a resistor?" -- I don't understand your question.
 
Last edited:
  • #3
How do I find resistance with that graph?
 
  • #4
You can't. R = 5ohm and C = 2μF will give you the same graph as R = 2ohm and C = 5μF. You might be able to find R if you know the inital current in the circuit, I0, which is equal to Vf/R.
 

1. How do you find the capacitance from a capacitor graph?

To find the capacitance from a capacitor graph, you will need to know the voltage and current values at different points on the graph. Then, you can use the formula C = Q/V, where C is the capacitance, Q is the charge, and V is the voltage. By rearranging the formula, you can solve for the capacitance.

2. What does the slope of a capacitor graph represent?

The slope of a capacitor graph represents the rate at which the voltage changes in relation to the charge. It is a measure of the capacitance of the capacitor, with a steeper slope indicating a higher capacitance and a flatter slope indicating a lower capacitance.

3. Can the capacitance be negative on a capacitor graph?

No, capacitance cannot be negative on a capacitor graph. Capacitance is a measure of the ability of a capacitor to store charge, and cannot have a negative value. If you come across a negative capacitance value on a graph, it is likely an error in measurement or calculation.

4. How does the shape of a capacitor graph change with different values of capacitance?

The shape of a capacitor graph will change based on the value of capacitance. A higher capacitance value will result in a steeper slope and a more gradual curve, while a lower capacitance value will result in a flatter slope and a sharper curve. The overall shape of the graph will still follow the same pattern, with voltage increasing as charge increases.

5. Why is it important to know the capacitance from a capacitor graph?

Knowing the capacitance from a capacitor graph is important because it is a crucial parameter in designing and using electronic circuits. The capacitance value determines how much charge can be stored in the capacitor and how quickly it can discharge. It also affects the behavior of the circuit and can impact its overall performance and stability.

Similar threads

  • Introductory Physics Homework Help
Replies
2
Views
770
  • Introductory Physics Homework Help
Replies
4
Views
910
  • Introductory Physics Homework Help
Replies
9
Views
198
  • Introductory Physics Homework Help
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
898
  • Introductory Physics Homework Help
Replies
4
Views
687
  • Introductory Physics Homework Help
Replies
7
Views
645
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
8
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
860
Back
Top