Capacitance and Electric Field

In summary, the capacitance of a capacitor is directly related to the amount of charge it can store. This means that a higher capacitance allows for a greater amount of stored energy. To increase capacitance, a dielectric can be inserted between the plates, which lowers the electric field and increases the capacity to store energy. However, this can lead to confusion as a lower electric field may seem counterintuitive for storing energy. It is important to consider whether the capacitor is connected to a battery, which keeps the potential difference constant, or if it is unconnected, which keeps the electric charge constant.
  • #1
EnchantedEggs
27
0
I've gotten myself in a bit of a muddle here, I'm hoping you lovelies can help me out!

So, the capacitance relates to the amount of charge a capacitor can store. Higher capacitance, greater charge. Greater stored charge, greater stored energy (right? or not?).

So a higher capacitance means you can store more energy in that capacitor. In order to increase the capacitance, we can insert a dielectric between the plates. This lowers the electric field between the plates and increases the capacitance.

If this is so, then a lower electric field results in a greater capacity to store energy? I must have gone wrong somewhere - I thought the whole point is that we're using an electric field to store potential energy. So surely a lower field means less stored energy? Argh!

Can someone clarify my muddled thinking a bit? I've been looking at articles and equations for hours now and I just seem to be making myself even more confused.
 
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  • #2
It makes a difference whether the capacitor is connected to a battery, so the potential difference across it is constant, so the electric field will also be constant, or whether it is unconnected, so the electric charge is constant.
 

FAQ: Capacitance and Electric Field

What is capacitance and how is it related to electric field?

Capacitance is the ability of a system to store an electric charge. It is defined as the ratio of the magnitude of the charge on one of the conductors to the potential difference between them. It is related to electric field by the equation C = Q/V, where C is capacitance, Q is charge, and V is potential difference. This means that the greater the capacitance, the more charge can be stored for a given potential difference.

How is capacitance calculated for different shapes and configurations?

The capacitance of a system depends on the geometry of the conductors and the material between them. For parallel plate capacitors, the capacitance is calculated using the equation C = εA/d, where ε is the permittivity of the material between the plates, A is the area of the plates, and d is the distance between them. For other configurations, such as cylindrical or spherical capacitors, the equations will be different.

What is the role of dielectric materials in capacitance?

Dielectric materials are insulators that are placed between the conductors of a capacitor. They are used to increase the capacitance of a system by reducing the electric field between the conductors. This is because the electric field is weaker in a dielectric material than in air or a vacuum. Dielectric materials also help to prevent current from flowing between the conductors, which can reduce the efficiency of the capacitor.

How does capacitance affect the behavior of circuits?

In DC circuits, capacitance causes a time delay or phase shift between the voltage and current. In AC circuits, capacitance can be used to store and release energy, which is useful in applications such as power factor correction and filtering. Capacitance also affects the impedance of a circuit, with higher capacitance resulting in lower impedance and vice versa.

How is capacitance measured and what units is it measured in?

Capacitance is measured using a device called a capacitance meter or a multimeter. The unit of capacitance is the farad (F), named after Michael Faraday, and is equal to one coulomb of charge per volt of potential difference. However, in most practical applications, capacitance is measured in smaller units such as microfarads (μF) or picofarads (pF).

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