Physics 4B

Physics 4B

1. Static electricity can be useful for restarting the heart when it has stopped (defibrillator)

2. Static electricity can be useful for electrostatic dust precipitators to remove smoke particles etc from chimneys:

   • 1. Metal plates/grids put into chimneys, with negative charge
     • 2. Dust particles gain electrons as they move through the grid
       • 3. (negative) dust particles attracted to earthed plates
         • 4. Dust falls back down chimney/removed at intervals

3. Key Processes

   • The metal grids in the electrostatic precipitator are given a high voltage. Depending on the design, the grids may be positively charged or negatively charged; dust particles lose electrons if the grids are positively charged and dust particles gain electrons if the grids are negatively charged. The charged dust particles then induce a charge on the earthed metal collecting plates and the dust particles are attracted to the plates
   • Paint Spraying
     • Car manufacturers can save money by using charged paint spray guns. They work because like charges repel and unlike charges attract. The spray gun is given a charge. This means that the droplets of point also become charged and they gain the same charge, so they repel each other and produce a fine spray. The car body part is given an opposite charge to the spray gun and paint droplets. This means the paint droplets are attracted to the body part, producing an even coat with little waste, even in awkward ‘shadow’ surfaces that the operator cannot see.
     • 1. The paint gun loses electrons so that it becomes positively charged
       • 2. The paint droplets lose electrons and so also become positively charged
         • 3. The object to be painted gains electrons and so becomes negatively charged
           • 4. The positively charged paint droplets repel each other and are attracted to the negatively charged surface
   • A defibrillator is a machine that can be used by paramedics to stabilise an irregular heartbeat. They work by discharging electric charge. Two paddles with insulated handles are charged from a high voltage supply. They are put in good electrical contact with the patient's chest. It is important that only the patient gets a shock: This is why the paddles have insulating handles. The operator and any one nearby stand clear. The defibrillator passes charge through the patient to make the heart contract