NTA Abhyas JEE Main2020PhysicsMagnetic Effects of CurrentPractice
Consider a region of space in which constant, uniform, and mutually perpendicular fields E → and B → exists. Now a particle of charge q enters this region with a velocity v → which is perpendicular to both the fields. If the velocity of the charge remains unchanged, then
Options
- Av → = B → × E → E 2
- Bv → = E → × B → B 2
- Cv → = B → × E → B 2
- Dv → = E → × B → E 2
Correct answer
B. v → = E → × B → B 2
Step-by-step solution
when E → and B → are perpendicular and velocity has no change then q E = q v B i . e . , v = E B . The two forces oppose each other so, v is along v → × B → i . e . , v → = E → × B → B 2 As E → and B → are perpendicular to each other E → × B → B 2 = E B sin 90 o B 2 = E B