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Why does the ratio of the voltage to current in capacitor and inductor depend on frequence?
Wiki User
∙ 13y ago
The ratio of voltage to current, or the impedance, of reactive elements such as capacitors and inductors depends on the frequency of the applied wave because they store energy, and the amount of energy they store is directly related to the frequency of the applied waveform.
When a DC voltage is applied to a capacitor, the current through the capacitor initially will be large, and will decay down to zero as the capacitor charges. Also, the voltage across the capacitor will be small initially and will increase over time to be equal to the applied voltage. This behavior results in a varying impedance when an AC waveform is applied. At a very low frequency, the capacitor will charge up and discharge similarly to if a DC source was switched into the capacitor for a long period of time there would be a large voltage drop, and small current = high impedance). As the frequency increases, the capacitor will appear more like a DC source was initially switched into the capacitor (low voltage drop and high current = low impedance).
Wiki User
∙ 13y ago
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What is the reason behind the lag of current in inductor lead in capacitor?
The physics of the energy storage. In an inductor, the current must fight against the stored energy in the magnetic field which tries to keep the current unchanged. Any change in the current lags the voltage since the stored energy impacts the adjustment. Similarly, the "displacement" current in a capacitor leads the electric field buildup in a capacitor, causing the voltage to lag the current until the stored energy building up in the electric field stabilizes. Any change in the voltage is first preceded by a change in the displacement current.
Explain the function of the capacitor and inductor in a power supply?
A capacitor resists a change in voltage (dv/dt = i/c). An inductor resists a change in current (dl/dt = vl). Together, a capacitor and inductor make a tuned circuit. Usually, in a linear power supply, there is a capacitor in parallel with an inductor in series, and often, in a pi filter, another capacitor in parallel. This reduces the peak to peak voltage at the output. It is also possible to put an inductor in series with the rectifier diode, as as to reduce inrush current. In a switching power supply, things are a little bit different. The primary inductor is a current pump, maintaining constant current flow to the load, controlled by the pulse-width oscillator which switches between on-current from source and off-current from schottky diode. The capacitor in this case filters the output, so as to reduce high frequency harmonics.
How can current lag or lead voltage in an AC circuit isn't current a function of voltage etc?
Current can lag or lead voltage in an AC circuit when the load is what we call reactive. The idea that current is purely a function of voltage only applies when working with DC, or when working with purely resistive loads, such as light bulbs and toasters. Not so, when dealing with motors and power supplies. What happens is that an inductor resists a change in current. That means that, given a particular voltage and current at a particular instant of time, if you change the voltage, the current will not immediately follow - it will lag - because the inductor is a stored energy device. Similarly, a capacitor resists a change in voltage, which means that if you change the current, the voltage will not immediately follow - it will lag - also because the capacitor is a stored energy device. Flip over current and voltage in the analysis of a capacitor, and you find that the current will lead the voltage, as opposed to the inductor's current lagging the voltage. This causes the phenomenon of power factor, which is basically the cosine of the phase angle between voltage and current. Power factor is the ratio of apparent power to true power.
How do you find whether it is inductor or capacitor if only power factor is given?
in case of inductor or capacitor power factor is always zero.as power factor is cosine of phase angle between voltage and current. in case of inductor and capacitor phase angle between voltage and current is 90 so it become zero so if given power factor is zero then it can be inductor or capacitor.
Why the voltage drop across inductance and voltage drop across capacitance is greater than source voltage in series resonance circuit?
The reason for the total voltage drops across the capacitance and inductance IN AN AC CIRCUIT has to do with the different phase angles of the voltages.First, current is the same value and same phase angle everywhere in a series circuit. But, voltage across a capacitor lags current by 90 degrees (capacitor current leads voltage). Next, voltage across a pure inductance leads current by 90 degrees (inductor current lags voltage).The rule that all voltages in a series circuit have to add to the supply voltage still applies, but in this case, the voltage drops are added VECTORALLY, not arithmetically. If you were to graph this addition, you would show any resistance voltage in phase with the current, the capacitor voltage at -90 degrees to the current and the inductor voltage at +90 degrees to the current, for a phase difference between them of 180 degrees, cancelling each other out.In a series resonant circuit, the impedances of the capacitor and inductor cancel each other. The only impedance to the flow of current is any resistance in the circuit. Since real-life inductors always have some resistance, at least there is always some resistance in a series resonant circuit.
What are the abcs of electricity?
voltage current resistance power inductor capacitor Learning them, you got abc
What is difference among resistor capacitor and inductor?
In an AC circuit through a resistor the voltage and current are said to be in phase. Ie on the oscilloscope in the sine wave as the voltage rises so does the current in tandem. Through an inductor an electromagnetic field is created in the coil which produces a back emf which acts against any change in voltage. This slows down any sharp change in voltage as when a circuit is energised. With an inductor the voltage and current are out of phase. The voltage is said to lead over the current. It is displaced by 90 degrees. It is ahead of the current by 90 degrees on the sine wave. Through a capacitor the current rises until it is fully charged and then no more current flows. An AC current is constantly changing direction at 50 Hz in the UK. Through a capacitor the current leads over the voltage by 90 degrees in the sine wave. A capacitor can balance out the effect of the inductor. The inductor decreases the power factor, the capacitor increases the power factor. With an inductor a circuit draws more current, with a capacitor the current draw decreases. P=IxVxPf. Where Pf is the power factor or power correction factor. Factories will have a big capacitor to correct the power factor for induction motors. This improves the electrical efficiency and lowers the electric bill!
What is the difference between an inductor and a capacitor?
Firstly the suffix '-ance' in each of those three words indicate the properties the material exhibits. Therefore resistance is the property by which any material tends to oppose the flow of current through it. Inductance is the property by which a material opposes the change in current, or opposes an alternating current. An inductor can be appreciated simply using a coil of insulated wire, or a solenoid. Capacitance is the property by which a material opposes the change in voltage across its ends, ie how it opposes alternating voltage. A capacitor comprises of, essentially, two metallic plates separated by a dielectric (a medium which may/may not be non-conducting, but is capable to contain charge). cheers!!
What is the reason behind the lag of current in inductor lead in capacitor?
The physics of the energy storage. In an inductor, the current must fight against the stored energy in the magnetic field which tries to keep the current unchanged. Any change in the current lags the voltage since the stored energy impacts the adjustment. Similarly, the "displacement" current in a capacitor leads the electric field buildup in a capacitor, causing the voltage to lag the current until the stored energy building up in the electric field stabilizes. Any change in the voltage is first preceded by a change in the displacement current.
Explain the function of the capacitor and inductor in a power supply?
A capacitor resists a change in voltage (dv/dt = i/c). An inductor resists a change in current (dl/dt = vl). Together, a capacitor and inductor make a tuned circuit. Usually, in a linear power supply, there is a capacitor in parallel with an inductor in series, and often, in a pi filter, another capacitor in parallel. This reduces the peak to peak voltage at the output. It is also possible to put an inductor in series with the rectifier diode, as as to reduce inrush current. In a switching power supply, things are a little bit different. The primary inductor is a current pump, maintaining constant current flow to the load, controlled by the pulse-width oscillator which switches between on-current from source and off-current from schottky diode. The capacitor in this case filters the output, so as to reduce high frequency harmonics.
Why there's high voltage at series rlc resonant frequency?
With a series RLC circuit the same current goes through all three components. The reactance of the capacitor and inductor are equal and opposite at the resonant frequency, so they cancel out and the supply voltage appears across the resistor. This means that the current is at its maximum, but that current, flowing through the inductor and the capacitor, produces a voltage across each that is equal to the current times the reactance. The voltage magnification is the 'Q factor', equal to the reactance divided by the resistance.
How can current lag or lead voltage in an AC circuit isn't current a function of voltage etc?
Current can lag or lead voltage in an AC circuit when the load is what we call reactive. The idea that current is purely a function of voltage only applies when working with DC, or when working with purely resistive loads, such as light bulbs and toasters. Not so, when dealing with motors and power supplies. What happens is that an inductor resists a change in current. That means that, given a particular voltage and current at a particular instant of time, if you change the voltage, the current will not immediately follow - it will lag - because the inductor is a stored energy device. Similarly, a capacitor resists a change in voltage, which means that if you change the current, the voltage will not immediately follow - it will lag - also because the capacitor is a stored energy device. Flip over current and voltage in the analysis of a capacitor, and you find that the current will lead the voltage, as opposed to the inductor's current lagging the voltage. This causes the phenomenon of power factor, which is basically the cosine of the phase angle between voltage and current. Power factor is the ratio of apparent power to true power.
Is there no induced voltage in an inductor unless the current is changing?
In an ideal inductor, no, there is no voltage induced across an inductor unless the current in the inductor is changing. However, since there are no ideal inductors nor power supplies, eventually an inductor will draw a constant current, i.e. the limit of the power supply; and, since no inductor has zero ohms at equilibrium, that current will translate to voltage.
How do you find whether it is inductor or capacitor if only power factor is given?
in case of inductor or capacitor power factor is always zero.as power factor is cosine of phase angle between voltage and current. in case of inductor and capacitor phase angle between voltage and current is 90 so it become zero so if given power factor is zero then it can be inductor or capacitor.
What is the phase angle between voltage and current in a purely capacitive circuit?
Current leads voltage (or voltage lags current) by 90° in a purely capacitive circuit. Try to remember it this way: capacitors resist change in voltage, hence the voltage lags (they resist voltage change because the voltage first goes to charging up the electric field in the capacitor).Inductors resist change in current (energy in an inductor is in the form of magnetic fields, which are caused by the current through the wire). Remember an inductor is a coil (like an electromagnet, or a transformer).
Why voltage leads current in a inductor?
Eli the ice man. Voltage (E) before Current (I) in a coil (inductor)(L) Current (I) before Voltage (E) in a Cap. (C) Got it?
Capacitor inductor circuit which smooth out rectified ac voltage are known as?
filter circuits
