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where resistance in ohms and capacitance in farads yields the time constant in seconds or the cutoff frequency in hertz (Hz). The cutoff frequency when expressed as an angular frequency ( ω c = 2 π f c ) {\displaystyle (\omega _{c}{=}2\pi f_{c})} is simply the reciprocal of the time constant.
where C is the capacitance of the capacitor. Solving this equation for V yields the formula for exponential decay: =, where V 0 is the capacitor voltage at time t = 0. The time required for the voltage to fall to V 0 / e is called the RC time constant and is given by, [1]
Capacitance is proportional to the area of overlap and inversely proportional to the separation between conducting sheets. The closer the sheets are to each other, the greater the capacitance. An example is the capacitance of a capacitor constructed of two parallel plates both of area separated by a distance .
As a result, device admittance is frequency-dependent, and the simple electrostatic formula for capacitance, = , is not applicable. A more general definition of capacitance, encompassing electrostatic formula, is: [6]
In addition, these equations assume that the electric field is entirely concentrated in the dielectric between the plates. In reality there are fringing fields outside the dielectric, for example between the sides of the capacitor plates, which increase the effective capacitance of the capacitor. This is sometimes called parasitic capacitance.
In electrical circuits, reactance is the opposition presented to alternating current by inductance and capacitance. [1] Along with resistance, it is one of two elements of impedance; however, while both elements involve transfer of electrical energy, no dissipation of electrical energy as heat occurs in reactance; instead, the reactance stores energy until a quarter-cycle later when the energy ...
A Maxwell bridge is a modification to a Wheatstone bridge used to measure an unknown inductance (usually of low Q value) in terms of calibrated resistance and inductance or resistance and capacitance. [1] When the calibrated components are a parallel resistor and capacitor, the bridge is known as a Maxwell bridge.
resistance – conductance; voltage division – current division; impedance – admittance; capacitance – inductance; reactance – susceptance; short circuit – open circuit; Kirchhoff's current law – Kirchhoff's voltage law. KVL and KCL; Thévenin's theorem – Norton's theorem