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Why capacitor make 90 degree phase shift between voltage and current?
Wiki User
∙ 14y ago
To answer this we assume that the current in a passive component can be written as:
i(t) = I*cos(wt +phi), where I is the constant current amplitude
for a resistor:
V=IR, v(t) = A*R*cos(wt+phi)
thus, V = I*R angle(phi)
for a capacitor:
i(t) = C*(dv/dt)
v(t) = V*cos(wt +phi)
dv/dt = V*w*sin(wt +phi)
therefore:
i(t) = wCV*sin(wt + phi)
v(t) = V*cos(wt +phi)
from this it is clear that the current in a capacitor is 90degrees out of phase (sin->cos 90degrees difference) and that the current amplitude is dependent on capacitance value and frequency (w=2*pi*f).
remember because capacitors are not ideal the 90degree phase shift will vary and be dependent on paracitic elements such as parallel/series resistance and series inductance.
Wiki User
∙ 14y ago
Wiki User
∙ 11y agois capistor = capacitor the below one is my answer.
Yes. When alternating current flows through a capacitor voltage lags current by 90 degrees.
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Why does the current lead the voltage across a capacitor by 90 degree rather than lag it?
A: Because a capacitor have to have time to charge to the voltage In a capacitor, the current depends on the voltage difference across it. On AC, this makes it charge, if the voltage is increasing above zero, and discharge if the voltage is reducing towards zero. Because a capacitor has almost no internal resistance, and most loads that it is connected to have only very small resistances in series with the capacitor, the charging and discharging currents depend pretty much on the rate at which the voltage is changing. At the zero crossing point of the sine-wave, when the voltage is actually zero, the rate of change of voltage is very high (the sine-wave is at its steepest), so the current is also very high. If the voltage is positive-going, the current is positive, and if the voltage is negative-going, the current is negative. At the peak of the voltage waveform, the rate of change of voltage is zero or very low (the sine-wave is flat, and not really changing its voltage) so the current is zero, too. Since the maximum positive current occurs when the voltage is passing through zero, going positive, and the maximum negative current happens when the voltage is passing through zero, going negative, the current peaks happen 90 degrees before the voltage peaks, so the current is said to lead the voltage. This is the same as saying the voltage lags the current by 90 degrees.
How can a capacitor reduce the effects of ripple voltage?
The smoothing capacitor converts the full-wave rippled output of the rectifier (which is left over AC signal) into a smooth DC output voltage A smoothing capacitor after either a half-wave or full-wave rectifier will be charged up to the peak of the rectified a.c. Between peaks of the a.c. the stored voltage will drop by a degree dependent on how much current is drawn from it by the load. The larger the value of the capacitor, the less drop there will be, and therefore less ripple when loaded.
How can a capacitor raise the voltage level?
A capacitor alone can not raise the voltage level.Capacitors together with a multivibrator (Or an AC source) and some diodes can do the trick. Works well on higher voltages.Capacitors together with a multivibrator and an inductor would be the preferred method for low voltages. It works well even on voltages as low as 0.8 Volt.Capacitors and diodes are by far the easiest available components.Have a look at the related link down below for more information on how to raise the voltage.
In a pure inductance circuit the current lags the voltage by what degree?
90 degrees
What effect capacitor has on alternating current ac?
In the basic configuration, a capacitor is constructed with two parallel conductor plates with a layer of insulating material in between. When the cap is hooked up to the AC power supply, the voltage (v) across the plates and the charge (q) induced on the plates follow this capacitance expression: C = dq/dv or i = C dv/dt, where C is determined by the properties of the insulating material and the geometry of the cap (in the case of the parallel plates, the separation between the two electrodes (t). For the parallel plates, C can be written as (dielectric constant * plate area / t). Electrically, the change in the charge induced on the plates (dq), is directly related to the change in voltage difference (dv) between the two plates, since C is a constant. Theoretically, no energy is lost by charging and discharging the cap with an AC current. When the cap absorbs electrical energy from the power supply, it stores the energy in the electric field in the insulator. When discharging, the cap gives the stored energy back to the circuit -- hence, no energy loss. In a circuit, we use the cap to prolong/smoothen/resist any voltage change in time or to absorb a sudden energy surge (electrostatic discharge and power-line glitches, for example).
Relation between voltage and current if you consider capacitor ckt?
In a capacitor ckt, current will be lead ahead from voltage by an angle 90 degree. Because for a capacitor the relationship between voltage and current is given as v=(jx)i , where v= voltage i= current jx=capacitive reactance
Why does the current lead the voltage across a capacitor by 90 degree rather than lag it?
A: Because a capacitor have to have time to charge to the voltage In a capacitor, the current depends on the voltage difference across it. On AC, this makes it charge, if the voltage is increasing above zero, and discharge if the voltage is reducing towards zero. Because a capacitor has almost no internal resistance, and most loads that it is connected to have only very small resistances in series with the capacitor, the charging and discharging currents depend pretty much on the rate at which the voltage is changing. At the zero crossing point of the sine-wave, when the voltage is actually zero, the rate of change of voltage is very high (the sine-wave is at its steepest), so the current is also very high. If the voltage is positive-going, the current is positive, and if the voltage is negative-going, the current is negative. At the peak of the voltage waveform, the rate of change of voltage is zero or very low (the sine-wave is flat, and not really changing its voltage) so the current is zero, too. Since the maximum positive current occurs when the voltage is passing through zero, going positive, and the maximum negative current happens when the voltage is passing through zero, going negative, the current peaks happen 90 degrees before the voltage peaks, so the current is said to lead the voltage. This is the same as saying the voltage lags the current by 90 degrees.
How can a capacitor reduce the effects of ripple voltage?
The smoothing capacitor converts the full-wave rippled output of the rectifier (which is left over AC signal) into a smooth DC output voltage A smoothing capacitor after either a half-wave or full-wave rectifier will be charged up to the peak of the rectified a.c. Between peaks of the a.c. the stored voltage will drop by a degree dependent on how much current is drawn from it by the load. The larger the value of the capacitor, the less drop there will be, and therefore less ripple when loaded.
The phase angle between voltage and current in an a c circuit through a pure capacitance is?
90 DEGREE
What does it mean to have a power factor of 1?
First we need to know what is power factor ? it's cosine of angle between the current and voltage at that point where we wish to measure it. so power factor of "1" means the angle between the voltage and current is 0 degree. It means literally that the current and voltage is in the same phase.
What is lead and lag angles?
Leading angle means that the current lead voltage by 90 degree,which implies a capacitve load. while,lagging angle mean when the current lag the voltage by 90 degree or when the voltage lead the current by 90 degree.which implies an inductive load.
What determine the flow of charge through a conductor?
Charges may appear to flow through a capacitor, although in reality they don't.The degree to which charge appears to flow through a capacitor depends on therate at which the voltage across it changes.-- DC voltage doesn't change, so it doesn't appear to pass through a capacitor at all.-- AC voltage is always changing, and the higher its frequency, the more currentit appears to push through a capacitor.
How can a capacitor raise the voltage level?
A capacitor alone can not raise the voltage level.Capacitors together with a multivibrator (Or an AC source) and some diodes can do the trick. Works well on higher voltages.Capacitors together with a multivibrator and an inductor would be the preferred method for low voltages. It works well even on voltages as low as 0.8 Volt.Capacitors and diodes are by far the easiest available components.Have a look at the related link down below for more information on how to raise the voltage.
If the voltage applied across a capacitance is triangular in waveform then the waveform of the current?
Depend the value of capacitor. Capacitance in series act like a high pass filter, while in parallel act like low pass filter. By fourier series, triangular wave is combine of series of the sine or cosine waves. Therefore by certain capacitance, sine wave can preduce by applied a triangular signal through a capacitor. Current is just 90 degree shift from voltage, shape is same.
In a pure inductance circuit the current lags the voltage by what degree?
90 degrees
What is a correction factor capacitor?
i know that static capacitors are used to improve the power factor. power factor should be high. Static capacitor supplies lagging reactive power. That means; the current I has 2 components they are magnetising Im (watless or waste current) and useful current Iw. Iw is in phase with voltage and Im is 90 degree away. Phase angle between them is phi 1. power factor is given by cosine of phi 1. phi angle should be less so that cosine of phi is high. To make phi angle less we use capacitor; this is nothing but power factor correction and capacitor used for this is called power factor correction capacitor. now when a capacitor is connected, it induces a current Ic 180 out of phase from Im and less in magnitude from Im. therefore, now the magnetising current is Im1=Im-Ic. due to this the phase angle reduces to phi 2. now the new power factor is cosine of phi 2. it is improved power factor.
What effect capacitor has on alternating current ac?
In the basic configuration, a capacitor is constructed with two parallel conductor plates with a layer of insulating material in between. When the cap is hooked up to the AC power supply, the voltage (v) across the plates and the charge (q) induced on the plates follow this capacitance expression: C = dq/dv or i = C dv/dt, where C is determined by the properties of the insulating material and the geometry of the cap (in the case of the parallel plates, the separation between the two electrodes (t). For the parallel plates, C can be written as (dielectric constant * plate area / t). Electrically, the change in the charge induced on the plates (dq), is directly related to the change in voltage difference (dv) between the two plates, since C is a constant. Theoretically, no energy is lost by charging and discharging the cap with an AC current. When the cap absorbs electrical energy from the power supply, it stores the energy in the electric field in the insulator. When discharging, the cap gives the stored energy back to the circuit -- hence, no energy loss. In a circuit, we use the cap to prolong/smoothen/resist any voltage change in time or to absorb a sudden energy surge (electrostatic discharge and power-line glitches, for example).
