In an ink-jet printer, an ink droplet of mass m is given a negative charge q by a compute

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1. Electric Charges and Fields

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In an ink-jet printer, an ink droplet of mass $m$ is given a negative charge $q$ by a computer-controlled charging unit, and then enters at speed $v$ in the region between two deflecting parallel plates of length $L$ separated by distance $d$ (see figure below). All over this region exists a downward electric field which you can assume to be uniform. Neglecting the gravitational force on the droplet, the maximum charge that can be given so that it will not hit a plate is close to :

A

$\frac{mv^2E}{dL^2}$

B

$\frac{mv^2d}{EL^2}$

C

$\frac{md}{E(vL)^2}$

D

$\frac{m(vL)^2}{Ed}$

Solution

$\mathrm{a}=\frac{\mathrm{q} \mathrm{E}}{\mathrm{m}}$

$\frac{\mathrm{d}}{2}=\frac{1}{2}\left(\frac{\mathrm{qE}}{\mathrm{m}}\right) \mathrm{t}^{2}$

$t=\frac{L}{v}$

Standard 12

Physics

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