A charged particle would continue to move with a constant velocity in a region wherein,

1. \(E=0, ~B\ne0\)
2. \(E\ne0, ~B\ne0\)
3. \(E\ne0, ~B=0\)
4. \(E=0, ~B=0\)

Choose the correct option:
1. (a), (c)
2. (b), (d)
3. (b), (c), (d)
4. (c), (d)

(2) Hint: Find the Lorentz in each case.
Step 1: Here, the force on the charged particle due to the electric field, FE=qE
Force on the charged particle due to the magnetic field, Fm=qv×B
Step 2: Now, FE=0ifE=0andFm=0ifsinθ=0orθ°=0°or180°
Hence, B ≠ 0
Also, E = 0 and B = 0 and the resultant force, q E + q (v x B) = 0. In this case E ≠ 0 and B ≠ 0.