NEETPhysicsMagnetic Effects of Current
A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. Match the particles and their initial projection directions in List-I with their resulting trajectories and kinetic energy changes in List-II. List-I List-II (A) Proton projected parallel to the fields (P) Straight line, kinetic energy increases (B) Electron projected parallel to the fields (Q) Straight line
Options
- A(A)-(P), (B)-(Q), (C)-(R), (D)-(S)
- B(A)-(Q), (B)-(P), (C)-(R), (D)-(S)
- C(A)-(P), (B)-(Q), (C)-(S), (D)-(R)
- D(A)-(R), (B)-(Q), (C)-(P), (D)-(S)
Correct answer
A. (A)-(P), (B)-(Q), (C)-(R), (D)-(S)
Step-by-step solution
Let the electric field E and magnetic field B be along the x-axis. (A) Proton projected parallel to the fields: Velocity v is parallel to B , so magnetic force F_m = q( v B ) = 0 . The electric force F _e = e E acts in the direction of motion, causing the proton to accelerate in a straight line. Thus, its kinetic energy increases. (A) matches (P). (B) Electron projected parallel to the fields: Velocity v is parallel to B , so F_m = 0 . The electric force F _e = -e E acts opposite to the direction of motion, causing