Physics - Uses of Electrostatics

Static electricity is used in many ways, including spray painting, smoke precipitators and defibrillators.

Spray Painting                                                                              The paint particles are given a negative charge so that they repel each other, forming a fine spray. This  ensures that the paint is applied evenly. The panel to be sprayed ins positively charged so it attracts the negatively charged paint. This means that less paint is wasted and even the back and sides of the object, in the shadows of the spray, receive a coat of paint.

In a similar way, electrostatics can be used in crop-spraying.

The paint gains electrons as it passes through the nozzle of the gun, so becomes negatively charged. The car panel has lost electrons so is left positively charged, The car attracts the oppositely charged paint. As the paint sticks to the car, the charges cancel so the car becomes neutrally charged and no more paint is attracted. The car receives and even amount of paint.

Electrostatic dust precipitors can remove smoke particles from chimneys. Metal grids are installed in the chimney and are connected to a high potetial difference (voltage). The dust becomes positively charged as it passes the grid, including a positive charge on the dust, The dust particles are attached to the negativecharged plates, where they form large particles that fall back down the chimney when they are heavy enough, or if the plates are stuck,

The dust particles become charged when they lose electrons.

Electricity can be used to start the heart when it has stopped. Two paddles are charged and are put in a good electrical contract with the patient's chest using gel. Taking care not to shock the operator, charge is then passed through the patient to make the heart contract.