A proton moving with a constant velocity passes through a region of space without any change in its velocity. If $\vec{E}$ and $\vec{B}$ represent the electric and magnetic fields respectively, then the region of space may have :
(A) E = 0, B = 0
(B) E = 0, B ≠ 0
(C) E ≠ 0, B = 0
(D) E ≠ 0, B ≠ 0 Choose the most appropriate answer from the options given below :
Options

Question

A proton moving with a constant velocity passes through a region of space without any change in its velocity. If $\vec{E}$ and $\vec{B}$ represent the electric and magnetic fields respectively, then the region of space may have :
(A) E = 0, B = 0
(B) E = 0, B ≠ 0
(C) E ≠ 0, B = 0
(D) E ≠ 0, B ≠ 0 Choose the most appropriate answer from the options given below :

Options

G1 Physics · Accepted Answer

For the proton to move with constant velocity, net force must be zero: qE⃗ + q(v⃗ × B⃗) = 0 Possible cases are: (i) E = 0 and B = 0 (ii) E = 0, B ≠ 0 and v⃗ × B⃗ = 0 (iii) E ≠ 0 and B ≠ 0 such that qE⃗ = -q(v⃗ × B⃗) Thus (A), (B) and (D) are possible. Correct option: C.