How Can RMS Current Be Represented as a Phasor?

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RMS current represents the effective value of alternating current, which can be expressed as a phasor in AC circuits. While RMS is a scalar value, it can be associated with a phasor that includes a phase angle, indicating the relationship between voltage and current. In inductive circuits, the current lags behind the voltage due to self-inductance, which introduces a phase difference. The discussion emphasizes that the RMS value can be used to describe the magnitude of the phasor, but it does not inherently make RMS a phasor itself. Understanding the context and notation in textbooks is crucial for correctly interpreting these concepts.
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If RMS current is equal to the value of the direct current that would produce the same power dissipation in a resistive load, how can it be phasor?
 
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In which type of circuits you have encountered complex voltages...
i think in AC circuits the elements may not dissipate energy but act as storage devices and are related by phase difference, there in the analysis the instant voltages may be complex.
 
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drvrm said:
In which type of circuits you have encountered complex voltages...
i think in AC circuits the elements may not dissipate energy but act as storage devices and are related by phase difference, there in the analysis the instant voltages may be complex.
I'm sorry I mean RMS currect, i'd edited the title and yeah I mean AC circuit
 
Zheng_ said:
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I'm sorry I mean complexcurrect, i'd edited the title and yeah I mean AC circuit
What I'm asking is RMS currect. I know that voltage and currect in AC circuit can be phasor, but why RMS current, which descibe a effective value, can be a phasor? It wouldn't change its value as the time is passing right?
 
Zheng_ said:
What I'm asking is RMS currect. I know that voltage and currect in AC circuit can be complex number, but why RMS current, which descibe a effective value, can be a phasor?

the phase angle contains z the reactance which is complex

Suppose we have an inductive circuit, and here the voltage and current waves are not in-phase. Whenever a changing voltage is applied to an inductive coil, a “back” e.m.f. is produced by the coil due to its self-inductance. This self-inductance opposes and limits any changes to the current flowing in the coil.Further the effect of this back e.m.f. is that the current wave form reaches its peak value some time after that of the voltage. The current always “lags” behind the voltage .
 
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drvrm said:
the phase angle contains z the reactance which is complex

Suppose we have an inductive circuit, and here the voltage and current waves are not in-phase. Whenever a changing voltage is applied to an inductive coil, a “back” e.m.f. is produced by the coil due to its self-inductance. This self-inductance opposes and limits any changes to the current flowing in the coil.Further the effect of this back e.m.f. is that the current wave form reaches its peak value some time after that of the voltage. The current always “lags” behind the voltage .
Ok thanks
 
But who said that the RMS value of the current is a phasor? You represent the variable quantities (current, voltage) by phasors.
The RMS value is just this, a value. Of course, you can take the magnitude of the phasor representing the current equal to the RMS value.

Same as the magnitude of the velocity vector is equal to the speed. This does not make speed a vector.
 
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nasu said:
But who said that the RMS value of the current is a phasor? You represent the variable quantities (current, voltage) by phasors.
The RMS value is just this, a value. Of course, you can take the magnitude of the phasor representing the current equal to the RMS value.

Same as the magnitude of the velocity vector is equal to the speed. This does not make speed a vector.
But..one of the question in my homework let that I rms = 2∠10°?
 
That may be but it's hard to say what they mean without context. It may be just a notation to say that the magnitude of the phasor is equal to the RMS value and has a phase angle of 10 degrees.
The conventions for notations depend on the specific textbook. Read the chapter about phasors and pay attention to the meanings of the notations.
 
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nasu said:
That may be but it's hard to say what they mean without context. It may be just a notation to say that the magnitude of the phasor is equal to the RMS value and has a phase angle of 10 degrees.
The conventions for notations depend on the specific textbook. Read the chapter about phasors and pay attention to the meanings of the notations.
Ok thanks. I will go and read through my textbook.
 
  • #11
rms is a 'scaling factor'...all voltages in AC circuits (VR, VL and Vc can be quoted as rms, or average or maximum or whatever else.
This does not affect the angular relationship between these quantities...the phasor aspect of their representation.
It would be wise to be consistent
 
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Zheng_ said:
But..one of the question in my homework let that I rms = 2∠10°?
This tells you the current is i(t) = 2√2⋅sin(ωt+10°)
 
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