Find the value of a capacitor given percent of the initial value

In summary, the formula for finding the value of a capacitor given a percentage of its initial value is Vf = Vi * (1 - p/100). It is important to find the value of a capacitor in terms of its initial value in order to understand its degradation over time and determine if it needs to be replaced. The percentage in the formula represents the amount of the initial value that is still present in the capacitor. It can be used for any initial value, but assumes a linear degradation. Without knowing the initial value, it is impossible to accurately determine the current value of the capacitor.
  • #1
rocapp
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Homework Statement



A capacitor is discharged through an 80.0 ohm resistor. The discharge current decreases to 23.0% of its initial value in 1.50ms .

What is the value of the capacitor?

Homework Equations



t=RC

The Attempt at a Solution



1500 μs = 0.23 RC
RC= 6521.74

C= 6521.74/R

C= 6521.74/80 = 81.5 μF


This is not correct... Please help! It's due within the next thirty minutes!
 
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  • #2
The voltage vs time graph is not linear.
$$v(t)=V_0e^{-t/RC}$$
 

Related to Find the value of a capacitor given percent of the initial value

1. How do I calculate the value of a capacitor given a percentage of its initial value?

The formula for finding the value of a capacitor given a percentage of its initial value is Vf = Vi * (1 - p/100), where Vf is the final value, Vi is the initial value, and p is the percentage.

2. Why is it important to find the value of a capacitor in terms of its initial value?

Finding the value of a capacitor in terms of its initial value allows us to understand the degradation of the capacitor over time. It also helps us determine if the capacitor is still functioning properly and if it needs to be replaced.

3. What is the significance of the percentage in determining the value of a capacitor?

The percentage represents the amount of the initial value that is still present in the capacitor. It helps us understand how much the capacitor has degraded over time and how much of its original capacity is still usable.

4. Can I use the same formula for calculating the value of a capacitor with different initial values?

Yes, the formula is applicable for any initial value as long as the percentage is given. However, it is important to note that the formula assumes a linear degradation of the capacitor over time, which may not always be the case.

5. Is there a way to determine the value of a capacitor without knowing its initial value?

No, the initial value is necessary in order to accurately determine the current value of the capacitor. Without knowing the initial value, it is impossible to calculate the percentage of the initial value that is still present in the capacitor.

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