Static electricity

• What is static electricity?


  Static electricity is the build-up of charge on insulating materials.
• What causes sparks in static electricity?


  Sparks occur when static electricity is discharged.
• What do all materials contain that contributes to charge?

  All materials contain positive protons and negative electrons.
• Why are most materials neutral overall?

  Because the positive and negative charges cancel each other out.
• What happens when materials are rubbed together?

  Friction causes electrons to be rubbed off one material and onto the other.
• How do conducting materials behave with static electricity?


  In conducting materials, electrons can flow back, preventing charge build-up.
• What happens in insulating materials when rubbed?


  Electrons cannot flow back, leaving a positive charge on the material that lost electrons.
• What is an example of an insulating material mentioned?

  A polythene rod.
• What happens when a cloth rubs against an acetate rod?

  The acetate rod loses electrons and becomes positively charged, while the cloth gains electrons and becomes negatively charged.
• What is the key point to remember about static charge transfer?


  Only negative electrons are transferred, not positive protons.
• What occurs if an object keeps gaining negative electrons?


  A potential difference develops between the charged material and the earth.
• What is the potential difference of earth objects?


  Earth objects are always at zero volts.
• What happens if the potential difference is large enough?


  Electrons can jump across the gap, creating a spark.
• Can charges build up on conductors?


  Yes, charges can build up on conductors, but it is less common.
• How can cars build up charge?


  Cars can build up charge due to their metal frame being in contact with the wind.
• What happens when you touch a charged car?


  You may experience a small spark as the car discharges to the earth through your body.
• What is the process of charge transfer when rubbing materials together?


  • Rubbing causes friction.
  • Electrons are transferred from one material to another.
  • One material becomes positively charged (loses electrons).
  • The other material becomes negatively charged (gains electrons).
• What are the differences between conductors and insulators in terms of static electricity?

  Conductors:

  • Electrons can move freely.
  • Charge does not build up significantly.

  
  

  Insulators:

  • Electrons cannot move freely.
  • Charge can build up significantly.
• What is one danger of electrostatic charges?


  Static charges pose a risk of electric shock.
• What happens when a person touches an object with a large amount of static charge?


  Electrons will flow through the person's body to the earth.
• Why is it dangerous when aircraft and tankers build up static charge on the vehicle or pump when fuelling?

  It can create a spark that could ignite fuel which is extremely flammable, causing fire or explosion.
• What safety measure can be taken to prevent static charge from igniting fuel during refueling?


  An earthing wire can be attached to allow charge to flow into the earth.
• What is the purpose of earthing in relation to electrostatic charges?

  • Offers electrons an alternative pathway to the earth
  • Prevents the buildup of static charge on the surface of the insulator
  • Less electrostatic charge reduces the risk of electric shock
• What are the dangers of electrostatic charges ?

  Static charges pose a risk of electric shock. If a person touches an object with a large amount of static charge, electrons will flow through the person's body to the earth.
• What is two use of electrostatic charges in technology?

  In inkjet printers and photocopiers
• What happens in an inkjet printer?


  In an inkjet printer, droplets of ink are charged and pass between two charged metal plates, one of which has a positive charge and the other a negative charge. The droplets are attracted to the plate with the opposite charge and repelled by the plate with the same charge and deflected towards a specific place on the paper.
• What happens in a photocopier?

  In a photocopier, the image of a document is projected onto a positively charged plate; where light falls onto the plate, the charge leaks away. Negatively charged toner particles are attracted to the remaining positive areas. Paper is then placed over the plate and the toner is transferred to it, making the photocopy.