Conductor

• the capacitor displays its true characteristics only when a change in the voltage or current is made in the network
• The Electric Field


  This electric field is represented by electric flux lines, which are drawn to indicate the strength of the electric field at any point around the charged body.
• The denser the lines of flux, the stronger is the electric field.
• electric flux lines always extend from a positively charged body to a negatively charged body, always extend or terminate perpendicular to the charged surfaces, and never intersect.
• electric field strength is directly related to the size of the charge Q. The greater the charge Q, the greater is the electric field intensity on a unit charge at any point in the neighborhood.
• Capacitance is a measure of a capacitor’s ability to store charge on its plates—in other words, its storage capacity.
• the higher the capacitance of a capacitor, the greater is the amount of charge stored on the plates for the same applied voltage.
• The unit of measure applied to capacitors is the farad (F), named after an English scientist, Michael Faraday,
• The greater the charge Q, the greater is the electric field intensity on a unit charge at any point in the neighborhood
• the pattern is a direct result of the fact that electric flux lines strive to establish the shortest path from one charged body to another.
• The flux lines tend to establish a buffer action between the two with a repulsive action that grows as the two charges are brought closer to one another
• Capacitance is a measure of a capacitor’s ability to store charge on its plates—in other words, its storage capacity.
• the higher the capacitance of a capacitor, the greater is the amount of charge stored on the plates for the same applied voltage.
• fringing that occurs at the edges as the flux lines originating from the points farthest away from the negative plate strive to complete the connection
• The equation for the electric field strength is determined by two factors only: the applied voltage and the distance between the plates.
• permittivity is applied as a measure of how easily a material “permits” the establishment of an electric field in the material.
• . The voltage required per unit length is an indication of its dielectric strength and is called the breakdown voltage.
• When breakdown occurs, the capacitor has characteristics very similar to those of a conductor
• typical example of dielectric breakdown is lightning, which occurs when the potential between the clouds and the earth is so high that charge can pass from one to the other through the atmosphere (the dielectric).
• maximum working voltage


  This is the highest voltage that the capacitor can handle continuously without getting damage
• The basic components of a capacitor are: conductive plates, separation, and dielectric.
• Larger plates permit an increased area for the storage of charge, so the area of the plates should be in the numerator of the defining equation.
• The smaller the distance between the plates, the larger is the capacitance, so this factor should appear in the numerator of the equation.
• Finally, since higher levels of permittivity result in higher levels of capacitance, the factor should appear in the numerator of the defining equation
• Capacitors, like resistors, can be listed under two general headings: fixed and variable.
• fixed capacitor


  Fixed-type capacitors come in all shapes and sizes
• the larger the required capacitance, the larger is the physical size of the capacitor
• This factor, however, is very sensitive to how thin the dielectric can be made, with natural concerns because the working voltage (the breakdown voltage) drops as the gap decreases.
• The charging phase—the phase during which charge is deposited on the plates
• This period of time during which charge is being deposited on the plates is called the transient period—a period of time where the voltage or current changes from one steady-state level to another.
• the voltage across a capacitor in a dc network is essentially equal to the applied voltage after five time constants of the charging phase have passed.
• the transient or charging phase of a capacitor has essentially ended after five time constants.
• the current of a capacitive dc network is essentially zero amperes after five time constants of the charging phase have passed.
• during the charging phase, the major change in voltage and current occurs during the first time constant.
• A capacitor can be replaced by an open-circuit equivalent once the charging phase in a dc network has passed.
• a capacitor has the characteristics of a short-circuit equivalent at the instant the switch is closed in an uncharged series R-C circuit
• The voltage across a capacitor cannot change instantaneously
• The larger the capacitance, the larger is the time constant, and the longer it will take the voltage across the capacitor to reach the applied value.
• The term t(0-) defines the instant just before a switch or action occurs.
• The time t(0+) is just after the change in state occurs.