RMS Current in an AC Generator with Doubled Rotational Speed

In summary, the output voltage of an a.c. generator is V = NBAωsin(ωt) and when connected across an inductor, the rms current is 10mA. If the rotational speed of the coil inside the generator is doubled, the reactance of the inductor changes but the rms current remains at 10mA due to the fact that it is independent of the rotation speed.
  • #1
Terocamo
47
0

Homework Statement


The output voltage of an a.c. generator is
[tex]\emph{V}[/tex]=[tex]\emph{NBA}[/tex][tex]\omega[/tex]sin([tex]\omega[/tex]t).
When the voltage is connected across an inductor, the rms current in the inductor is found to be 10mA. What will Be the rms current if the rotating speed of the coil inside the generator is doubled?

The Attempt at a Solution


I try to rearrange the equation, what i think is that the reactance of the inductor is constant so that if
Xc=[tex]\frac{NBA\omega}{\sqrt{2}Irms}[/tex] (strangely i cannot get the root 2 shown in the faction)
Then [tex]\omega\propto[/tex]Irms
So if the rotational speed doubles the Irms also doubled.
But however the answer is the reactance change and the rms current remains at 10mA.
I don't understand how these kind of question can be solved cause there isn't any constant I can make use of in the question...
 
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  • #2
Vmax = NABω and XL = ωL. Imax = Vmax/ωL = NAB/L.

When When the rotating speed doubles, Vmax = NAB(2ω) and XL= 2ωL

So Imax remains the same. Same is true for Irms.
 
  • #3
I don't understand. How is the reactance doubles but not the current?
 
  • #4
Terocamo said:
I don't understand. How is the reactance doubles but not the current?

Imax = Vmax/XL = NAB(2ω)/2ωL = NAB/L
 
  • #5
oic the current is independent of rotation speed, thanks.
 

1. What is RMS current in an AC generator with doubled rotational speed?

RMS current, or root mean square current, is the measure of the average amount of current flowing in an AC circuit. When the rotational speed of an AC generator is doubled, the RMS current also doubles.

2. How is RMS current related to the rotational speed of an AC generator?

RMS current is directly proportional to the rotational speed of an AC generator. This means that as the rotational speed increases, the RMS current also increases.

3. Why does the RMS current double when the rotational speed is doubled in an AC generator?

This is because the faster the generator rotates, the more rapidly the magnetic field changes, leading to a higher rate of change of current and therefore a higher RMS current.

4. What is the significance of RMS current in an AC generator?

RMS current is an important measure in an AC generator as it represents the amount of current that would produce the same amount of heat as an equivalent DC current. This allows for easier comparison and analysis of AC and DC systems.

5. How does doubling the rotational speed affect the power output of an AC generator?

Doubling the rotational speed of an AC generator also doubles the power output. This is because power is directly proportional to both the rotational speed and the RMS current in an AC generator.

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