Examples of electrostatics are all around us! One example is inkjet printing. In inkjet printing, very small droplets of ink are passed through a chamber where they become charged. These charges are then accelerated by a potential, and then steered with an electric field. Drop sizes of 0.09 mm diameter are typically used. The individual droplets are then charged directly by an electron gun to a charge of about 2 x10-10 C. These charged droplets are accelerated from essentially being at rest to a final speed of 20.2 m/s by a potential difference V. If we assume the ink drops have the same density as water, calculate the potential difference needed. Steering the drops (to make the final image we want) is done by electric fields between two parallel plates. The plates are 0.5 mm long and are 1.0 mm apart. The beam is input at the middle between the plates. The largest electric field necessary would be one that steers the beam enough just to make contact with the upper (or lower)plate. What potential difference between the plates is necessary? You can safely ignore any effects due to gravity as they are negligible.

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