In the figure, the three particles are fixed in place and have charges, $q_1=q_2=+5e$ and$q_3=+2e$ where the distance is, $a=3.00 \mathrm{\mu m}$. What are the,
(a) magnitude and
(b) direction of the net electric field at point$P$ due to the particles?

In figure, the four particles are fixed in place and have charges, $q_1=q_2=+5\mathrm{e}$ , $q_3=+3e$ and$q_4=-12e$ where, the distance is, $d=8.0$ $\mathrm{\mu m}$. What is the magnitude of the net electric field at point $P$ due to the particles?

 In Millikan's experiment, an oil drop of radius$1.64 \mathrm{\mu m}$ and density $0.851 \mathrm{g} {\mathrm{cm}}^{-3}$ is suspended in chamber$\mathrm{C}$ (as shown in figure) when a downward electric field of $3.20\times {10}^5 \mathrm{N} {\mathrm{C}}^{-1}$ is applied. (a) Find the charge on the drop. In terms of $\mathrm{e}$. (b) If the drop had an additional electron would it move upward or downward?

Figure (a) shows two charged particles fixed in place on an$x$- axis with separation$L .$ The ratio $\frac{{\mathrm{q}}_1}{{\mathrm{q}}_2}$ of their charge magnitudes is$4.00.$ Figure (b) shows the$x$  component  ${\mathrm{E}}_{\mathrm{net}. \mathrm{x}}$ of their net electric field along the$x$-axis just to the right of particle$2 .$ The$x$-axis scale is set by$x_s=15.0 \mathrm{cm}.$ $\left(\mathrm{a}\right)$ At what value of$x>0$ is $E_{\text{net.x }}$maximum?
$\left(\mathrm{b}\right)$ If particle$2$ has charge$-q_2=-3e$ , what is the value of that maximum?

An electron enters a region of uniform electric field with an initial velocity of $30 \mathrm{km} {\mathrm{s}}^{-1}$ in the same direction as the electric field which has magnitude, $E=50 \mathrm{N} {\mathrm{C}}^{-1}$.

(a) What is the speed of the electron$1.5 \mathrm{ns}$ after entering this region?
(b) How far does the electron travel during the $1.5 \mathrm{ns}$ interval?