Sparks

Sparks

1. Conductors

   • Metals are good electrical conductors
   • Insulators do not conduct electricity
     • Charge can be built up on insulators by friction

2. When rubbed with a duster

   • Acetate and perspex become positively charged
   • Polythene becomes negatively charged
     • Electrons are transfered from the duster to the rod by friction
     • the duster becomes postively charged

3. In a stable, neutral atom

   • Same number of protons and electrons

4. Electrostatic effects are due to the transfer of negatively charged electrons

5. A Van de Graaff generator

   • Collects charge on a metal dome
   • 1. a person places their hands on the dome when it is uncharged
     • 2.The dome is then switched on and the person becomes charged
       • 3. all of the hairs on the person gain the same charge
         • 4. like charges repel, so the hairs move away from each other.

6. Electric shock

   • occurs when a person becomes charged and then earthed
   • Can be avoided by-
     • Earthing objects using an earth wire
     • using insulating rubber mats to stop the build up of charge
     • wear shoes with insulating rubber soles so stop the body building up a charge due to friction.

7. The voltage that produces a current

   • Is dependent on the resitance
     • The resistance of the body varies

8. Anti-static devices

   • liquids, sprays or dusters
     • Carry away and prevent electric charge
   • Dryer sheets
     • used in tumble dryers to stop charge

9. Static electricity is dangerous

   • Inflammable gases or vapours
     • when they are present there is an increase in oxygen levels
     • A spark would ignite the gas or vapour and cause an explosion
   • When cleaning oil tankers their tanks are first filled with an inert gas such as nitrogen to avoid a spark that could cause an explosion
   • Mobile telephones must not be used in petrol stations to prevent sparks that could cause an explosion.

10. Static electricity is a nusiance

    • Dust and dirt are attracted to insulators, such as t.vs
    • Clothes made from synthetic materials often cling to the body