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My book shows this diagram in which electron moving only in magnetic field (where direction of magnetic field is out of the page) going down (after affecting by magnetic field) and hitting at point 'B'(not applying electric current/field). But according to Fleming's left hand rule the electron should go up(force due to magnetic field should push it up) and should hit at point 'A' (as direction of current is opposite from that of electrons).

electron moving in evacuated tube from anode to cathode

Here is the Fleming's left hand rule from my book

Fleming's left hand rule

illustration

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    $\begingroup$ Hi Supernova. Welcome to Phys.SE. If you want to use the textbook erratum tag, you should give precise reference. $\endgroup$
    – Qmechanic
    Sep 26, 2022 at 18:56

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The picture in your book contains an error. The magnetic field has to go into the other direction. Otherwise the electric and magnetic force cannot cancel each other and thus the experimental setup would not make much sense.

You can find a correct visualization of the experiment in Experiment 3: Mass-to-charge (e/m) ratio

You can clearly see that the north and south pole are swaped compared to your picture, whereas the electric field remains unchanged.

Well done! You´ve applied the Fleming´s left-hand rule correctly.

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If you use the conventional current direction you have to use your right hand. The left hand is used, if you take the first finger in direction of the moving electron. So your text should not just say "current" but electron movement.

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  • $\begingroup$ Ofcourse I'm using conventional current direction (which I think is opposite to the direction of electron). And the given rule in my book is in accordance with conventional current. if you're trying to say something else I'm sorry I didn't understand $\endgroup$
    – Super Nova
    Sep 26, 2022 at 17:49
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    $\begingroup$ I am sure that for conventional current going aginst the direction of electrons you have to use the right hand: pasco.com/products/guides/right-hand-rule $\endgroup$
    – trula
    Sep 26, 2022 at 18:00

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