On Jun 24, 1:33=A0am, "Don Kelly" <d...@[EMAIL PROTECTED]
> wrote:
> ----------------------------"Peter" <Poakfi...@[EMAIL PROTECTED]
> wrote in message
>
>
news:346cd631-7159-497e-a7aa-834fda352c9b@[EMAIL PROTECTED]
>
> > Hi! Can someone please help me? I understand the force in an electric
> > generator is F =3D B (q x v). Is the work done on the generator equal
t=
o
> > W =3D B(q x v) (vt), where vt is the distance the electrons in the
wire
> > move because of the rotation of the rotor? If the angular velocity of
> > the rotor is doubled, does the work done on the generator increase
> > four times, because it would then be W =3D B (q x 2v) (2vt); thus the
> > energy produced by the generator also increases four times? Thank.
> > Please excuse me if I am saying dumb things. I may be missing
> > something. I am trying to learn. Thanks.
>
> No. Note that force is q(v x B) not B (q x v) There is a difference. The
=
x
> is not a multiplication but a vector cross product. B and v are vectors
> while q is a scalar (-ve for electrons).
>
> It is easier to consider the case of a conductor of length l which is at
> right angles to the field and to the motion- then this is simplified.
> Then there is a force acting on the conductor of F=3DBli where i is the
> current (qv) and acting in a direction to oppose the motion - at right
> angles to the current.
> You can start from the same basis or use Faraday to determine the
voltage
> V=3DBlv
> The power of the generator will be Vi =A0which can be expressed as Fv
and=
the
> work in a given time will be the integral of this.
> If you double the velocity, you will double the =A0voltage but the
curren=
t
> will depend on =A0what is connected to the terminals of the
=A0generator.=
If
> open or short circuited, the work will be 0.
> In between with some load there will be some power.
>
> In the case of a fixed resistance load, doubling the speed, doubles the
> voltage and so quadruples the power (and energy in a given time). You
are
> right with respect to that although =A0your approach is not correct.
>
> Don Kelly d...@[EMAIL PROTECTED]
> remove the X to answer
Thank you. That helped a lot. Then, is it correct if I say the
instantaneous work done is W =3D q(v x B)(vt), where vt is the distance
and t is the time? (This is in analogy to W =3D force x distance.)
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