ECE-105 Chapter Notes - Chapter 3: Linear Variable Differential Transformer, Capacitor Types, Polypropylene

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9 Apr 2015

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Capacitors are constructed by separating two conducting plates, which are usually metallic, by a thin layer of insulating material. The insulating material between the plates, called a dielectric, can be air, Mylar, polyester, polypropylene, mica, or a variety of other materials. As current flows through a capacitor, charges of opposite signs collect on the respective plates. Positive charge on one plate is balanced by negative charge of equal magnitude on the other plate. In an ideal capacitor, the stored charge q is proportional to the voltage between the plates: capacitance c, which has units of farads (f). The relationship between current and voltage is. Charge as a function of time is given by. Voltage as a function of time is given by. Energy stored in the capacitance that can be returned to the circuit: Two alternative expressions for the stored energy: and. Capacitances in parallel are combined like resistances in series: Capacitances in series are combined like resistances in parallel:

Related Questions

Two parallel plates, each having area A = 2797cm2 areconnected to the terminals of a battery of voltage Vb = 6 V asshown. The plates are separated by a distance d = 0.53cm. You mayassume (contrary to the drawing) that the separation between theplates is small compared to a linear dimension of the plate.

1) What is C, the capacitance of thisparallel plate capacitor?

What is Q, the charge stored on the top plate of thethis capacitor?.

A dielectric having dielectric constant ? = 4.5 is nowinserted in between the plates of the capacitor as shown. Thedielectric has area A = 2797 cm2 and thickness equal to half of theseparation (= 0.265 cm) . What is the charge on the top plate ofthis capacitor?

What is U, the energy stored in thiscapacitor?

The battery is now disconnected from the capacitor andthen the dielectric is withdrawn. What is V, the voltage across thecapacitor?

To understand the meaning of capacitance and ways of calculating capacitance.

When a positive charge q is placed on a conductor that is insulated from ground, an electric field emanates from the conductor to ground, and the conductor will have a nonzero potential V relative to ground. If more charge is placed on the conductor, this voltage will increase proportionately. The ratio of charge to voltage is called the capacitance C of this conductor: C=q/V.

Capacitance is one of the central concepts in electrostatics, and specially constructed devices called capacitors are essential elements of electronic circuits. In a capacitor, a second conducting surface is placed near the first (they are often called electrodes), and the relevant voltage is the voltage between these two electrodes.

This tutorial is designed to help you understand capacitance by assisting you in calculating the capacitance of a parallel-plate capacitor, which consists of two plates each of area A separated by a small distanced with air or vacuum in between. In figuring out the capacitance of this configuration of conductors, it is important to keep in mind that the voltage difference is the line integral of the electric field between the plates.

Assume that charge -q is placed on the top plate, and +q is placed on the bottom plate. What is the magnitude of the electric field E between the plates?
What is the voltage V between the plates of the capacitor?

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An air-filled parallel-plate capacitor with capacitance Co stores the charge Q on plates separated by distance d. The potential difference across the plates is ΔV_o and the energy stored is U_o. If the capacitor is disconnected from its voltage source and the space between the plates is then filled with a dielectric of constant x = 2.00, evaluate the ratios (a) C_new/Co, (b) ΔV_new/ΔV_o, and (c) PE_newl PE₀•

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ECE-105 Chapter Notes - Chapter 3: Linear Variable Differential Transformer, Capacitor Types, Polypropylene

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