Capacitance and voltage relationship

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Homework Help Overview

The problem involves understanding the relationship between capacitance and voltage for a capacitor, specifically regarding the manufacturer's specified variance in capacitance values. The original poster is trying to determine the actual capacitance range for a capacitor rated at 1000 µF with a maximum percentage difference of -10% to +50%.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of the capacitance range based on the given percentage differences and question the interpretation of the variance as it relates to voltage versus capacitance.

Discussion Status

Some participants are exploring the calculations for the minimum and maximum capacitance values, while others are questioning the assumptions made about the relationship between voltage and capacitance. There is an acknowledgment of confusion regarding the terms used and their implications.

Contextual Notes

There is mention of the original poster's limited knowledge of capacitors, which may affect their understanding of the problem. Additionally, the discussion highlights a potential misinterpretation of the term "percentage difference" in the context of the problem.

jsmith613
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Homework Statement



The actual value of the capacitor Rahal will receive may be different from the value the
catalogue states. The manufacturer guarantees that the maximum percentage difference
below/above the catalogue value will be –10% / +50%. Rahal orders one of the 400 V 1000 µF capacitors. Within what range will its actual value lie?

Homework Equations



Q=CV
therefore C is inversely proportional to V

The Attempt at a Solution



I would say:
1100µF = max
500µF = min

BUT THE ANSWER IS
900µF = min
1500µF = max

WHY?

thanks
 
Last edited:
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The stated capacitance is 1000.

The possible variance is -10% to +50%.

What is 10% of 1000 subtracted from 1000?
What is 50% of 1000 added to one thousand?
 
Martinet said:
The stated capacitance is 1000.

The possible variance is -10% to +50%.

What is 10% of 1000 subtracted from 1000?
What is 50% of 1000 added to one thousand?

but the variance is for the voltage...
 
jsmith613 said:
but the variance is for the voltage...

Where is that stated?
If so, why is the answer given farads?

Additionally, bearing in mind that I'm yet to study capacitors in any level of detail, does the voltage not correspond to a maximum input voltage that the device can handle without being damaged, destroyed, or at least cease to function?
 
Martinet said:
Where is that stated?
If so, why is the answer given farads?

Additionally, bearing in mind that I'm yet to study capacitors in any level of detail, does the voltage not correspond to a maximum input voltage that the device can handle without being damaged, destroyed, or at least cease to function?

The manufacturer guarantees that the maximum percentage difference
below/above the catalogue value will be –10% / +50%.
 
Are you reading "percentage difference" as "percentage potential difference" or something similar?
 
Martinet said:
Are you reading "percentage difference" as "percentage potential difference" or something similar?

yes...oops
thanks
 

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