Re: Can electromagnets push?


OK Don, thanks for the answer.

As I've said in another group, this is all first year university
physics but that year is about 12 year away by now :) In my case at
least.

In any case, it's always important to hear another man's opinion, be it
positive or negative, but always substantiated, elaborated,
scientifically provable and with references. That's what "peer review"
is for.

Regards,
Marko


Don Kelly wrote:
----------------------------
<marko.horvat@xxxxxxxx> wrote in message
news:1154074043.847627.50990@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi,

A question for anyone who can provide some proof or bibliographic
references behind the answer:

Let's assume that we have a solenoid, i.e. an electromagnet -
conductor wire wrapped around a hollow core with alternating current
flowing through it and generating a magnetic field perpendicular to the
wire's orientation according to the Faraday's law.

The solenoid is fixed and mounted on a mobile superstructure, e.g. a
cart. Let's also assume there is no friction between the
superstructure and its base.

Now if we take some charged particles, like ions or electrons, with the
mass m, and accelerate them through the solenoids core increasing their
velocity by delta v, will the solenoid and its base experience a force
in the opposite direction according to the Newton's Third Law of
Motion? In a nutshell, will the electromagnet move if it accelerates
charged particles?

And please, some scientific references to/against the proof would be in
order.

Thanks,
Marko

Look up Lorentz's Law (the scientific basis of 3 finger motor/generator
rules) . The magnetic force will be dependent on the cross product of
velocity (cross) B. This will mean some vector analysis is needed(look it
up). In the case where the velocity of the charge is at an angle a with
respect to the field B then the force =charge*velocity magnitude * field
magnitude* sin ( a)
In your example, with the direction of the charge motion in the same
direction as the field- result is 0, no acceleration - as sin a =a=0. The
cart won't move either.
If the direction of the field is perpendicular to the direction that the
charge is moving, then the force will be perpendicular to both and a
maximum. The acceleration will be perpendicular to the motion so that the
direction of motion will change but the magnitude of the velocity won't. The
charge will try to go in circles. (Look up electron Ballistics ).

.--

Don Kelly dhky@xxxxxxxxxxxx
remove the X to answer



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