Question

In an inkjet printer,1 tiny drops of ink of inertia m are given a charge q and then fired toward the paper at speed v. They first pass between two charged plates of length l that create an (approximately) uniform electric field of magnitude E between them. The field direction is perpendicular to the plates and to the initial path of the drops. The electric field deflects each drop from its initial horizontal path and is used to control what is printed on the paper. (a) Show that the amount of vertical deflection is given by ∆y = 1 2 (q/m)(l/v) 2E (ignoring gravity). (b) For a drop of inertia 1.5 × 10−10 kg, an electric field strength of 1.2 × 106 N/C, a plate of length 10 mm, and a drop speed of 20 m/s, calculate the drop charge necessary to result in a deflection of 1.3 mm. (c) What will be the drop’s speed as it leaves the region between the plates? (d) Is it acceptable to ignore gravity here? Why?

Answer 1