Magnetic Effects Of Current Question 4
Question 4 - 2024 (27 Jan Shift 1)
A proton moving with a constant velocity passes through a region of space without any change in its velocity.
If $\overrightarrow{\mathrm{E}}$ and $\overrightarrow{\mathrm{B}}$ represent the electric and magnetic fields respectively, then the region of space may have :
(A) $\mathrm{E}=0, \mathrm{~B}=0$
(B) $\mathrm{E}=0, \mathrm{~B} \neq 0$
(C) $\mathrm{E} \neq 0, \mathrm{~B}=0$
(D) $\mathrm{E} \neq 0, \mathrm{~B} \neq 0$
Choose the most appropriate answer from the options given below :
(1) (A), (B) and (C) only
(2) (A), (C) and (D) only
(3) (A), (B) and (D) only
(4) (B), (C) and (D) only
Show Answer
Answer: (3)
Solution:
Net force on particle must be zero i.e. $q \vec{E}+q \vec{V} \times \vec{B}=0$
Possible cases are
(i) $\overrightarrow{\mathrm{E}} & \overrightarrow{\mathrm{B}}=0$
(ii) $\overrightarrow{\mathrm{V}} \times \overrightarrow{\mathrm{B}}=0, \overrightarrow{\mathrm{E}}=0$
(iii) $q \vec{E}=-q \vec{V} \times \vec{B}$
$\overrightarrow{\mathrm{E}} \neq 0 & \overrightarrow{\mathrm{B}} \neq 0$
