What is a Helmholtz coil?

At a place, an electric field and a magnetic field are in the downward direction. There an electron moves in the downward direction. Hence this electron.____________.

A velocity selector consists of electric field $\overrightarrow{E}=E \hat{\mathrm{k}}$ and magnetic field $\overrightarrow{B}=B \hat{\mathrm{j}}$ with $B=12 \mathrm{mT}$. The value $E$ required for an electron of energy $728\mathrm{eV}$ moving along the positive $\mathrm{x}$-axis to pass undeflected is 

(Given, mass of electron $=9.1\times {10}^{-31} \mathrm{kg}$)

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

A particle a mass of ${10}^{-2} \mathrm{kg}$ carries a charge of $5\times {10}^{-8}\mathrm{C}$. The particle is given an initial horizontal velocity of ${10}^5{ \mathrm{ms}}_{}^{-1}$ in the presence of electric field $\overrightarrow{E}$ and magnetic field $\overrightarrow{\mathrm{B}}$. To keep the particle moving in a horizontal direction, it is necessary that

(i) $\overrightarrow{B}$ should be perpendicular, to the direction of velocity and $\overrightarrow{E}$ should be along the direction of velocity.

(ii) Both $\overrightarrow{B}$ and $\overrightarrow{E}$ should be along the direction of velocity.

(iii) Both $\overrightarrow{B}$ and $\overrightarrow{E}$ are mutually perpendicular and perpendicular to the direction of velocity.

(iv) $\overrightarrow{B}$ should be along the direction of velocity and $\overrightarrow{E}$ should be perpendicular to the direction of velocity.

Which one of the following pairs of statements is possible?

This question is about the velocity selector shown in figure.

Calculate the speed of an ion emerging from the slit $S$ when the magnetic flux density is $0.30 T$ and the electric field strength is $1.5\times {10}^{3 }V{m}^{-1}.$

This question is about the velocity selector shown in figure.

Explain why ions travelling with a speed greater than your answer to part (b) will not emerge from the slit.

This question is about the velocity selector shown in figure.

State the directions of the magnetic and electric forces on a positively charged ion travelling towards the slit $S$.