Voltage in Capacitor vs. Power Supply: Conceptual Question Answered

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In summary, the voltage in a capacitor can potentially be equal to or greater than the voltage in the power supply due to factors such as inductance, ringing, and thermal energy affecting the charge carriers. However, this is only possible in certain scenarios and is not a common occurrence.
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flyingpig
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Homework Statement




I am just wondering, can the voltage in a capacitor ever be equal to or greater than the voltage in the power supply? Probably not the power supply...but is it possible to be equal to?




The Attempt at a Solution

 
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In a real circuit where there's always a bit of inductance at play, sure. Inductance causes what might be taken as a sort of current momentum that can cause an "overshoot" of the charging "goal" potential difference. When there's more than just a whisper of inductance at play, you can get what's called a "ringing" after abrupt changes in driving voltage -- a decaying oscillation around the final value. This can be seen easily on an oscilloscope view of the voltage in a circuit, such as where a square wave is driving a circuit.

Even if there were no inductance, the capacitor voltage can end up equal to the supply voltage +/- the effect of one unit elementary charge, since the charge carriers come in discrete size. Momentum coupled with random processes due to thermal energy will also slosh the charges around the equilibrium point to some extent.
 

1. What is the relationship between voltage in a capacitor and power supply?

The voltage in a capacitor is directly proportional to the power supply voltage. This means that if the power supply voltage increases, the voltage in the capacitor will also increase, and vice versa.

2. How does a capacitor store voltage?

A capacitor stores voltage through the build-up of electric charge on its two plates. When connected to a power supply, one plate becomes positively charged and the other becomes negatively charged, creating an electric field between them. This stored charge is what gives a capacitor its voltage.

3. Can a capacitor have a higher voltage than the power supply?

No, a capacitor cannot have a higher voltage than the power supply it is connected to. The capacitor's voltage is limited by the power supply voltage. However, in some cases, a capacitor can have a higher voltage rating than the power supply, meaning it can handle a higher voltage without breaking down.

4. How does the voltage in a capacitor change over time?

When connected to a power supply, the voltage in a capacitor increases over time as it charges up. However, if the power supply is disconnected, the voltage in the capacitor will slowly decrease over time as it discharges. The rate at which the voltage changes depends on the capacitance of the capacitor and the resistance in the circuit.

5. Can a capacitor hold a constant voltage?

Yes, a capacitor can hold a constant voltage as long as it is connected to a constant power supply. This is because the capacitor's charge will continuously adjust to maintain a constant voltage across its plates. However, if the power supply is changed or disconnected, the voltage in the capacitor will change accordingly.

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