Voltage & Capacitors: How Does It Create Charge?

In summary: You reminded me of another point of confusion...voltage is work/ charge... V = -W/q = (U2-U1)/q... since the difference in potential energy is equal to the negative of the work done. How do you relate those equations to this one concerning Electric energy storage in a capacitor? U = 1/2 QVBy definition, C = Q/V, i.e. 1 farad = 1 coulomb / volt. Then Q = CV. U = (1/2)QV = (1/2)(CV)V = (1/2) C V^2.
  • #1
gkangelexa
81
1
For a given capacitor that is connected to a battery, the amount of charge acquired by each plate is proportional to the magnitude of the potential difference V between them.
Q = CV

Is it correct to say that the voltage (potential difference V) applied across the capacitor plates is what causes the charge?
How does the voltage from the battery create the charge?


thanks!
 
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  • #2
No. Charge is a fundamental quantity, along with time, mass, & length. Voltage is a ratio of work to charge. Voltage from a to b is defined as the work per unit charge expended transporting a charge from a to b.

Charge is basic. Voltage is defined in terms of work & charge. Nothing "causes charge" that we know of. Charge just basically is & that's all we can say.

Claude
 
  • #3
Claude,
You reminded me of another point of confusion...
voltage is work/ charge... V = -W/q = (U2-U1)/q... since the difference in potential energy is equal to the negative of the work done.

How do you relate those equations to this one concerning Electric energy storage in a capacitor? U = 1/2 QV
 
  • #4
yes, we can say Potential differencce is cause for the charge but it does not mean that charge is created.

when a battery is connected to a circuit , the electrons are produced due to the chemical reactions in the battery .These electrons flow into the capacitor and the voltage
across the capacitor rises until the supply voltage and the electrons flow stops .

once the capacitor is charged the voltage of the capacitor is same as that of the battery.
 
  • #5
gkangelexa said:
Claude,
You reminded me of another point of confusion...
voltage is work/ charge... V = -W/q = (U2-U1)/q... since the difference in potential energy is equal to the negative of the work done.

How do you relate those equations to this one concerning Electric energy storage in a capacitor? U = 1/2 QV

By definition C = Q/V, i.e. 1 farad = 1 coulomb / volt. Then Q = CV. U = (1/2)QV = (1/2)(CV)V = (1/2) C V^2.

Claude
 

FAQ: Voltage & Capacitors: How Does It Create Charge?

What is the difference between voltage and capacitance?

Voltage is the measure of the potential energy difference between two points in an electrical circuit. It is measured in volts and determines the strength of an electric field. Capacitance, on the other hand, is the ability of a material to store electric charge. It is measured in farads and depends on the material's physical properties and geometry.

How does voltage create charge in a capacitor?

When a voltage is applied to a capacitor, it creates an electric field between its two plates. This electric field attracts and stores opposite charges on each plate, creating an electric potential difference between them. This process continues until the capacitor is fully charged, and the voltage across it equals the applied voltage.

Can a capacitor hold a constant charge?

No, a capacitor cannot hold a constant charge. As the voltage across a capacitor changes, the charge on its plates also changes. However, the capacitance of a capacitor determines how much charge it can store for a given voltage, and this value remains constant.

What is the role of capacitance in electronic circuits?

Capacitors are essential components of electronic circuits. They are used to filter out unwanted frequencies, store energy, and stabilize voltage levels. They are also commonly used in timing circuits, as their charging and discharging rates can be precisely controlled.

How do voltage and capacitance affect the energy stored in a capacitor?

The energy stored in a capacitor is directly proportional to both the capacitance and the square of the voltage across it. This means that increasing either the capacitance or the voltage will result in more energy being stored in the capacitor. Conversely, decreasing either of these values will decrease the energy stored in the capacitor.

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