Why Does Induced EMF Change in Generators but Not Moving Conductors?

In summary: yup,in summary, the changing magnetic flux in a rotating generator induces a sinusoidal change in the induced voltage, while in a moving conductor, the induced voltage remains constant due to the constant velocity.
  • #1
leojun
26
0
why does induced emf change in case of generators but remains constant in case of moving conductor?
 
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  • #2
after thinking for a while,i myself came to the conclusion that constant change in magnetic flux(in moving conductor with constant vel) causes constant induced emf and sinusoidal change in magnetic flux(in rotating generator) causes sinusoidal induced emf...:);)
 
  • #3
The second part of your question is a bit confusing. A conductor does not generate constant emf if it moves at constant speed through a constant magnetic field. There has to be a time rate of change of flux enclosed by the conductor.

Induced voltage is governed by Faraday's law: [itex]\oint \vec{E}\cdot d\vec{s} = -\frac{d}{dt}\int \vec{B}\cdot d\vec{A}[/itex]

Since in a rotating generator, [itex]\vec{B}\cdot d\vec{A}[/itex] is integrated over the area enclosed by a conducting loop in the armature, the right side keeps changing if the loop rotates in a fixed magnetic field. So the induced voltage (the left side: the line integral of the electric field over the path around the loop) keeps changing.

If a conducting loop moves through a constant magnetic field there is no induced emf. This is because there is no change in the flux enclosed by the loop.

AM
 
  • #4
Andrew Mason said:
If a conducting loop moves through a constant magnetic field there is no induced emf. This is because there is no change in the flux enclosed by the loop.

AM

Not the whole loop moves, but one side only in the experiments showing induced voltage in a moving straight piece of metal.

ehild
 
  • #5
yup,the conductor here means the movable piece of metal...not the whole circuit.
 
  • #6
ehild said:
Not the whole loop moves, but one side only in the experiments showing induced voltage in a moving straight piece of metal.

ehild
Ok. So the "moving conductor" is really an expanding loop in which dA/dt = velocity x length of the conductor. In that case [itex]\xi = -\frac{d}{dt}\int\vec{B}\cdot d\vec{A}[/itex] = -Bvl which is constant if v is constant.

AM
 
  • #7
Andrew Mason said:
Ok. So the "moving conductor" is really an expanding loop in which dA/dt = velocity x length of the conductor. In that case [itex]\xi = -\frac{d}{dt}\int\vec{B}\cdot d\vec{A}[/itex] = -Bvl which is constant if v is constant.

AM
Yes.

ehild
 

1. Why does induced EMF change in generators?

Induced EMF changes in generators because of Faraday's law of electromagnetic induction. According to this law, a changing magnetic field can induce an electric current in a conductor. In generators, this changing magnetic field is created by the motion of the conductor through the magnetic field.

2. Why doesn't induced EMF change in moving conductors?

Induced EMF does not change in moving conductors because there is no relative motion between the conductor and the magnetic field. In order to induce an electric current, there must be a changing magnetic field. If the conductor is moving at a constant speed through the magnetic field, there is no change in the magnetic field and therefore no induced EMF.

3. What factors can affect the induced EMF in generators?

The magnitude of the induced EMF in generators can be affected by several factors, including the strength of the magnetic field, the speed of the conductor, and the angle between the conductor and the magnetic field. Additionally, the number of turns in the coil and the resistance of the circuit can also affect the induced EMF.

4. How does the direction of motion of the conductor affect the induced EMF?

The direction of motion of the conductor can determine the direction of the induced EMF. If the conductor is moving perpendicular to the magnetic field, the induced EMF will be at its maximum. If the conductor is moving parallel to the magnetic field, the induced EMF will be zero. The direction of the induced EMF can also be reversed by changing the direction of motion of the conductor.

5. Can the induced EMF in generators be increased?

Yes, the induced EMF in generators can be increased by increasing the speed of the conductor, increasing the strength of the magnetic field, or increasing the number of turns in the coil. However, there is a limit to how much the induced EMF can be increased, as too much current can damage the generator. Additionally, the resistance of the circuit can also affect the magnitude of the induced EMF.

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