0
Modern capacitors which have high capacitance in small size use a dielectric?
Wiki User
∙ 14y ago
Ceramic
Wiki User
∙ 14y ago
Add your answer:
Earn +20 pts
What will happen to the electric field of capacitor if temp of polarized dielectric is increased?
That will depend on the dielectric. There will be two main effects - any change in the permeativity of the dielectric, and thermal expansion which will increase the distance between the plates. There will also be an change (probably an increase), in leakage current through the dielectric. Any change is very likely to be small or insignificant - I have worked in a factory making capacitors and temperatures were very variable, not controlled, for measurements of capacitance.
Why capacitance increses in parallel?
To avoid that the plates touch each other. The better the dielectric, the closer the plates can be, thus making the electrostatic field on the opposite plates more intense, which allows for more electrons displaced via the charging circuit to the positive plate and more incomplete atoms (positive charges) left on the negative plate. Remember: Being the dielectric an isolator, there is NEVER current through the capacitor.
What is the effect of dielectric on the capacitance of a capacitor?
Any variation of the charge within a p-n diode with an applied voltage variation yields a capacitance wich must be added to the circuit model of a p-n diode. The capacitance associated with the charge variation in the depletion layer is called the junction capacitance, while the capacitance associated with the excess carriers in the quasi-neutral region is called the diffusion capacitance. Both types of capacitances are non-linear so that we will derive the small-signal capacitance in each case. We will find that the junction capacitance dominates for reverse-biased diodes, while the diffusion capacitance dominates in strongly forward-biased diodes. The total capacitance is the sum of both.
What happens to the capacitance when a conducting slab of thickness is partially placed in between?
If the slab is zero thickness, nothing. The lines of electric field not intercepted by the slab are unaffected, so what goes on there is unaffected. The part where the lines are intercepted is converted to two capacitors in series, and the charges on opposite sides of the slab are equal and opposite, equal to the charge on the parts original outer plates facing it. From the outside view of the world, nothing changes on the outer plates, so the capacitance is the same. If the plate is not zero thickeness, then the capacitors on that side become higher and so the total capacitance will increase, with significant distortions of field lines. <<>> For a parallel-plate capacitor with small spacing, so that fringing can be neglected, with a flat slab of dielectric, the new capacitance is easily calculated by noting that the electric flux D is continuous, and in the volume occupied by the dielectric the E-field is reduced by a factor equal to the relative permittivity. Thus the voltage is reduced for a given amount of charge and the capacitance increased. If the plate area is A and the spacing is s and the dielectric thickness d, then with a charge Q on the plates the electric flux is just D = Q/A. The electric field on a line between the plates is D/eps0 in the air and D/(eps0 x epsr) inside the dielectric. Therefore the voltage is D/eps0 x (s-d) from the two air paths plus D/(eps0 x epsr) x d from the dielectric path. So the capacitance in this case is given by: C = A x eps0 / [s - d(1 - 1/epsr)] So if d=0 or epsr=1, as they are when there is no dielectric, the capacitance reverts to the standard formula for parallel plates: C = A x eps0 / s
Why polar capacitors can store charge in one way only?
The reason that some capacitors are polarized has to do with their physical construction. A common type of polarized capacitor is the aluminum electrolytic capacitor. These capacitors use aluminum coated with a thin layer of aluminum oxide for one plate and a conductive solution as the other plate. This strategy yields very high capacitance in a small physical volume because the aluminum oxide dielectric layer can be made extremely thin. Unfortunately, this construction only allows bias in one direction (the aluminum with the aluminum oxide coating must be the anode) because reversing the bias causes the dielectric to break down. I believe that the chemical reaction that takes place is this: when the aluminum plate coated with aluminum oxide is given a negative charge, the Al+3 ions in the aluminum oxide are reduced back to aluminum metal (taking electrons from the plate). This liberates the oxygen from the aluminum oxide as a gas, which is why reverse-polarizing these capacitors produces out-gassing (and bursting of the physical package of the capacitor if there is no relief valve). Tantalum electrolytic capacitors have a conceptually similar design. The anode is a tantalum wire with an oxide layer as a dielectric. Subjecting these capacitors to reverse bias also breaks down the dielectric by reducing the tantalum ion back to tantalum metal.
Modern capacitors which have high capacitance in small size use a dielectric of?
mylar
What will happen to the electric field of capacitor if temp of polarized dielectric is increased?
That will depend on the dielectric. There will be two main effects - any change in the permeativity of the dielectric, and thermal expansion which will increase the distance between the plates. There will also be an change (probably an increase), in leakage current through the dielectric. Any change is very likely to be small or insignificant - I have worked in a factory making capacitors and temperatures were very variable, not controlled, for measurements of capacitance.
Define titanium oxide capacitors with diagram?
have a very high capacitance with a small physical size when used at a low temperature.
Why capacitance increses in parallel?
To avoid that the plates touch each other. The better the dielectric, the closer the plates can be, thus making the electrostatic field on the opposite plates more intense, which allows for more electrons displaced via the charging circuit to the positive plate and more incomplete atoms (positive charges) left on the negative plate. Remember: Being the dielectric an isolator, there is NEVER current through the capacitor.
How many volts can a capacitor hold. what would be the formula for a capacitor that holds 100 volts?
The working voltage of a capacitor depends on the nature of the dielectric and its thickness. Most capacitors are marked on the case e.g. 500V wkg. or just 150V. Small components are colour coded; the code will tell you the capacitance, and the wkg voltage.
Why only electrolytic capacitors are used for filter dc?
high capacitance better filtering, electrolytics have high capacitance per volume. however electrolytic have some parasitic inductance, so many small ceramic capacitors are distributed on cards near ICs as a final "cleanup" filter and switching noise suppressor.
What is the effect of dielectric on the capacitance of a capacitor?
Any variation of the charge within a p-n diode with an applied voltage variation yields a capacitance wich must be added to the circuit model of a p-n diode. The capacitance associated with the charge variation in the depletion layer is called the junction capacitance, while the capacitance associated with the excess carriers in the quasi-neutral region is called the diffusion capacitance. Both types of capacitances are non-linear so that we will derive the small-signal capacitance in each case. We will find that the junction capacitance dominates for reverse-biased diodes, while the diffusion capacitance dominates in strongly forward-biased diodes. The total capacitance is the sum of both.
What happens to the capacitance when a conducting slab of thickness is partially placed in between?
If the slab is zero thickness, nothing. The lines of electric field not intercepted by the slab are unaffected, so what goes on there is unaffected. The part where the lines are intercepted is converted to two capacitors in series, and the charges on opposite sides of the slab are equal and opposite, equal to the charge on the parts original outer plates facing it. From the outside view of the world, nothing changes on the outer plates, so the capacitance is the same. If the plate is not zero thickeness, then the capacitors on that side become higher and so the total capacitance will increase, with significant distortions of field lines. <<>> For a parallel-plate capacitor with small spacing, so that fringing can be neglected, with a flat slab of dielectric, the new capacitance is easily calculated by noting that the electric flux D is continuous, and in the volume occupied by the dielectric the E-field is reduced by a factor equal to the relative permittivity. Thus the voltage is reduced for a given amount of charge and the capacitance increased. If the plate area is A and the spacing is s and the dielectric thickness d, then with a charge Q on the plates the electric flux is just D = Q/A. The electric field on a line between the plates is D/eps0 in the air and D/(eps0 x epsr) inside the dielectric. Therefore the voltage is D/eps0 x (s-d) from the two air paths plus D/(eps0 x epsr) x d from the dielectric path. So the capacitance in this case is given by: C = A x eps0 / [s - d(1 - 1/epsr)] So if d=0 or epsr=1, as they are when there is no dielectric, the capacitance reverts to the standard formula for parallel plates: C = A x eps0 / s
What is the unit of measure for capacitance?
The Farad is used to measure capacitance. Most small electronic capacitors are in microFarads(uF) or picoFarads (pF). The unit is name after Michael Faraday, the English chemist and physicist.
How does electrolytic capacitors work?
In an electrolytic capacitor the dielectric is a thin corrosion layer formed on the surface of a metal plate, the other plate of the capacitor is a moist electrolyte paste. This very thin dielectric allows electrolytic capacitors to have very high values of capacitance in small packages, but has two disadvantages: low breakdown voltage & polarization of the capacitor. It is very important that the polarity of an electrolytic capacitor not be reversed. If the polarity is reversed the thin corrosion layer erodes until the capacitor has no dielectric and shorts out, allowing electrolyses to produce hydrogen and oxygen gas in the moist electrolyte paste. The gas pressure eventually rises to the point that the case ruptures and the capacitor explodes.
Why polar capacitors can store charge in one way only?
The reason that some capacitors are polarized has to do with their physical construction. A common type of polarized capacitor is the aluminum electrolytic capacitor. These capacitors use aluminum coated with a thin layer of aluminum oxide for one plate and a conductive solution as the other plate. This strategy yields very high capacitance in a small physical volume because the aluminum oxide dielectric layer can be made extremely thin. Unfortunately, this construction only allows bias in one direction (the aluminum with the aluminum oxide coating must be the anode) because reversing the bias causes the dielectric to break down. I believe that the chemical reaction that takes place is this: when the aluminum plate coated with aluminum oxide is given a negative charge, the Al+3 ions in the aluminum oxide are reduced back to aluminum metal (taking electrons from the plate). This liberates the oxygen from the aluminum oxide as a gas, which is why reverse-polarizing these capacitors produces out-gassing (and bursting of the physical package of the capacitor if there is no relief valve). Tantalum electrolytic capacitors have a conceptually similar design. The anode is a tantalum wire with an oxide layer as a dielectric. Subjecting these capacitors to reverse bias also breaks down the dielectric by reducing the tantalum ion back to tantalum metal.
Difference between electrolytic and non-electrolytic capacitors?
Electrolytic Capacitors:1. It provides high capacitance in small volume.2. It has got polarity.3. It is not suitable for high frequencies due to losses in dielectrics.4. It is generally available in 1-100 µF rangeNon-Electrolytic Capacitors:1. Its capacitance depends on dielctric constant of the bulk.2. It doesn't have polarity.3. It is widely used at all frequencies.4. It ranges from pico Farads to fractions of µF.
