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# electromagnetic induction. watch

1. guys quick question!
if a horizontal rod aligned along a line from east to west and being dropped through a horizontal magnetic field which is directed from south to north. would the velocity of the rod be pointing down as the rod has been dropped?and to realise what end of the rod is positive, we should consider what the middle finger which is pointing at the west and it's the direction of emf which is the positive ?
any help would be great as I'm not sure if I'm correct or not!thanks
2. Could it be that you meant that experiment ?

In general whenever a rod which contains negative charge (electons) comes into a magnetic field - in a vertical position to it - the named negative charge is distracted, thus electrons are collected on one of two ends of the rod. That is why two different polarities come into being on both ends. And so, last but not least, the rod begins to move in a direction with a certain velocity (dropped as you wrote sounds a bit strange).

There is the so called right-hand-rule. In this case the thumb stands for the direction of the rod, the forefinger for magnetic field and the long finger for the force which distracts the electrons (lorentz force).

Here is a picture of it.

Let us find out the direction of the force and the rod by this rule! bend your fingers as in the picture. Show with your forefinger to the north. That is your direction of the magnetic field. Where is the direction of the longfinger? that is right, downwards, so the force as well (which distracts the electrons!). Where is the direction of the thumb from your view? on the right side! that is the direction of your rod and your velocity.

3. how about if your forfinger point to the north and your long finger pointing down which means your tumbs directed at the left, how do you realise which way you should point your finger here?
4. (Original post by Alen.m)
how about if your forfinger point to the north and your long finger pointing down which means your tumbs directed at the left, how do you realise which way you should point your finger here?
Oh, my mistake. You are right. By using the right hand the thumb shows in the left direction instead of the right one. I admit that I have used my left hand... how embarrassing.

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