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Because in an AC circuit, a capacitor opposes the change of voltage in at. At the peak of the voltage waveform, there is no change (it is nearly flat), so at this same point in time, the current waveform is at zero.
Likewise, when the voltage waveform crosses zero, it is changing at its fastest rate, so the current is at its peak.
If you draw these two waveforms next to one another, you will see the voltage has the appearance of being behind the current - hence the term 'lag'.
What else can I help you with?
What cause the voltage t lead current in an ac circuit?
Voltage leads current or, more specifically current lags voltage, in an inductive circuit. This is because an inductor resists a change in current.
How current lags the voltage in inductor?
In a perfect inductor (one with no series internal resistance), the current lags the voltage by 90 degrees. If the inductor has series internal resistance, then the current will lag the voltage by less than 90 degrees - the more the resistance in series with the inductor, the smaller the angle. The tangent of the angle can be found from the ratio of the inductive reactance of the inductor to the DC resistance of the inductor. That is, Tan (phase angle) = (2 x pi x frequency (Hz) x inductance (H)) divided by resistance (ohms) eg, a 1 henry, 100 ohm inductor on 60Hz would give: (2 x pi x 60 x 1) / 100 = 3.77; tan-1(3.77) gives 75 degrees lag of current behind voltage. The cosine of this angle gives the 'power factor' for the inductor - that is, the amount of useful energy dissipated in the inductor. Cos 75 is about 0.25 - so 25% of the energy actually does useful work (heat) - the rest of the energy (75%) is returned to the supply mains when the inductor discharges its magnetic field.
What is the power factor of an induction motor?
Induction motor comprised inductor as the most part in it and an inductor has the characteristic to oppose the change of current, i.e., it has lagging power factor as current lags behind the voltage. Hence, an induction motor works on lagging power factor.
What is the meaning of current lags voltage?
'Current lags voltage' means that in the AC cycle the voltage peaks and the current peaks a little time (a fraction of a cycle) later. This happens with electrical loads like motors. When the current lags, there is a small period in each half-cycle when the voltage has reversed and the current has not reversed yet. This causes power to flow back into the supply from the load. So there is a loss of average power fed to the load for a given voltage and current. In this situation the power is the voltage times the current times the power factor, and the power factor is the cosine of the angle by which the current lags the voltage (counting 360 degrees as a full cycle).
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.
What is the bahaviorS of the INDUCTOR in ac supply?
Because of Ac supply, current lags voltage by 90 in Inductor.
What cause the voltage t lead current in an ac circuit?
Voltage leads current or, more specifically current lags voltage, in an inductive circuit. This is because an inductor resists a change in current.
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).
What is the relationship between voltage and current in an inductive circuit?
Current lags voltage in an inductive circuit. The angle by which it lags depends on the frequency of the AC, and on the relative size of the inductance compared to the resistance in the circuit.
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 current lags the voltage in inductor?
In a perfect inductor (one with no series internal resistance), the current lags the voltage by 90 degrees. If the inductor has series internal resistance, then the current will lag the voltage by less than 90 degrees - the more the resistance in series with the inductor, the smaller the angle. The tangent of the angle can be found from the ratio of the inductive reactance of the inductor to the DC resistance of the inductor. That is, Tan (phase angle) = (2 x pi x frequency (Hz) x inductance (H)) divided by resistance (ohms) eg, a 1 henry, 100 ohm inductor on 60Hz would give: (2 x pi x 60 x 1) / 100 = 3.77; tan-1(3.77) gives 75 degrees lag of current behind voltage. The cosine of this angle gives the 'power factor' for the inductor - that is, the amount of useful energy dissipated in the inductor. Cos 75 is about 0.25 - so 25% of the energy actually does useful work (heat) - the rest of the energy (75%) is returned to the supply mains when the inductor discharges its magnetic field.
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?
What is the power factor of an induction motor?
Induction motor comprised inductor as the most part in it and an inductor has the characteristic to oppose the change of current, i.e., it has lagging power factor as current lags behind the voltage. Hence, an induction motor works on lagging power factor.
What does the voltage across a inductor do?
voltage across inductor create a flux. because of variation current developes an opposite emf.
What is the meaning of current lags voltage?
'Current lags voltage' means that in the AC cycle the voltage peaks and the current peaks a little time (a fraction of a cycle) later. This happens with electrical loads like motors. When the current lags, there is a small period in each half-cycle when the voltage has reversed and the current has not reversed yet. This causes power to flow back into the supply from the load. So there is a loss of average power fed to the load for a given voltage and current. In this situation the power is the voltage times the current times the power factor, and the power factor is the cosine of the angle by which the current lags the voltage (counting 360 degrees as a full cycle).
What is the maximum inductor voltage when the inductor current is decreasing?
depending on the stray capacitance it can be from a few ten volts to a few kilo volts.
What components comprise the excitation current of a transformer?
A transformer's excitation current can be resolved into two components. The first is in phase with the primary voltage, and is responsible for the losses. The second lags the supply voltage by 90 degrees, and is responsible for magnetising the core.
