Photocopiers
In photocopiers, there is an image plate which is positively charged, an image of what you are photocopying is then projected onto it. The charge leaks away from the white/light parts of what your copying as they make light fall on the plate. The dark/black parts of what your copying remain charged and attract negatively charged black power, which is transferred onto positively charged paper. Next, the paper is heated to stick the powder down.
Inkjet printers
In an inkjet printer, tiny droplets of ink are forced out of a fine nozzle, this makes them electrically charged. The droplets are then deflected as they pass between two metal plates. A voltage is applied to the plates, one is negative and the other is positive. The droplets are attracted the the plate of the opposite charge and repelled from the plate with the same charge - the size and direction of the voltage across each plate constantly changes so that each droplet is deflected to hit a different place on the paper.
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