Question

A proton (or charged particle) moving with velocity v is acted upon by electric field E and
magnetic field B. The proto will move undefeated if

1) E is perpendicular to B

2) E is parallel to v and perpendicular to B

3) E, B and v are mutually perpendicular and v=E/B

4) E and B both are parallel to v
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Answer 1

Answer:

...................

Answer 2

Answer:

GIVEN = velocity = v

electric feild = E

magnetic feild = B  

to find = v or position of  E ,V & V

solution :-

force due to magnetic feild = force due to electric feild

q( V × B ) = qE

V × B = E

so, E ,V & B are mutually perpendicylar and  VB =E ...........sin90°=1

so,option 3 that is ,  E, B and v are mutually perpendicular and v=E/B  is the correct answer.