Question

An ionized gas contains both positive and negative ions. If it is subjected simultaneously to an electric field along the $+x$ direction and a magnetic field along the $+z$ direction, then

• A. Positive ions deflect towards +y direction and negative ions towards -y direction
• B. All ions deflect towards +y direction
• C. All ions deflect towards -y direction
• D. Positive ions deflect towards -y direction and negative ions towards +y direction

Answer 1

Answer: (C)

As electric field will accelerate +ve charge along +ve x- axis and -ve charge along -ve x axis from $\overrightarrow{F}=\text{q}\left(\overrightarrow{v}\times \overrightarrow{B}\right)$ direction of $q(\overrightarrow{V}\times \overrightarrow{B})$ will be same for both of them i.e. $-vey$ direction so both will deflect towards $-vey$ direction.