Question 66: Magnetism and Matter

Question

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) $$\mathrm{E}=0, \mathrm{~B} 
eq 0$$
(C) $$\mathrm{E} 
eq 0, \mathrm{~B}=0$$
(D) $$\mathrm{E} 
eq 0, \mathrm{~B} 
eq 0$$
Choose the most appropriate answer from the options given below :

Accepted Answer

Net force on particle must be zero i.e.
$$\mathrm{q} \overrightarrow{\mathrm{E}}+\mathrm{q} \overrightarrow{\mathrm{V}} 	imes \overrightarrow{\mathrm{B}}=0$$
Possible cases are
(i) $$\overrightarrow{\mathrm{E}} \& \overrightarrow{\mathrm{B}}=0$$
(ii) $$\overrightarrow{\mathrm{V}} 	imes \overrightarrow{\mathrm{B}}=0, \overrightarrow{\mathrm{E}}=0$$
(iii) $$q \overrightarrow{\mathrm{E}}=-\mathrm{q} \overrightarrow{\mathrm{V}} 	imes \overrightarrow{\mathrm{B}}$$
$$\overrightarrow{\mathrm{E}} 
eq 0 \& \overrightarrow{\mathrm{B}} 
eq 0$$

Answer

(A), (B) and (C) only

Answer

(A), (C) and (D) only

Answer

(A), (B) and (D) only

Answer

(B), (C) and (D) only

Magnetism and Matter

Choose the correct answer: