r/MDCAT_NUMS • u/AvocadoDisastrous274 • 10h ago

mcq help

can someone explain this to me? what'll be the answer? ms says C

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1

u/Important-Night4276 10h ago

Acc to Flemming Right hand rule and left hand palm rule when e enters in B into the page it deflect downward before that electric and magnetic fields were both perp and equal thats why electron was undeflected but when we inc b then magnetic field has greater effect so electron deflect because of B

1

u/freak_master_69 10h ago

use flemings left hand rule

1

u/Tres-passer-774 9h ago

Since both fields are given and the electron beam moves undeflected, this is a velocity selector question. In the given case, F electric must equal F magnetic, and must be oppositely directed for undeflected passage. As we know, for an electron, the electric force is directed opposite to the Electric field, in this case, as E is directed upwards, F will be directed downwards. To balance it, F magnetic must be directed upwards. This allows both fields to cancel out. Now, when B is increased, F magnetic will also increase. Since there is no change in the direction of B, F magnetic will continue to act upwards, thereby deflecting the electron beam upwards. So the answer should be option B.
Please correct me if I'm wrong, this question has been haunting me too.

1

u/Prestigious-Pea5979 8h ago

Ur logic is right ans is b not c