static electricity

• static charge - friction

  certain insulating materials are rubbed against each other - become electrically charged

  • negatively charged electrons are rubbed off one material and on to the other.
  • the material that gains electrons becomes negatively charged.
  • the material that loses electrons is left with an equal positive charge
• two electrically charged objects are brought close together - exert a force on each other.

  • two objects that carry the SAME type of charge REPEL
  • two objects that carry DIFFERENT types of charge ATTRACT
  • attraction and repulsion between two charged objects = non-contact force.
• electric fields


  a charged object creates an electric field around itself
• where is the field strongest?

  close to the charged object
• where is the field weakest?

  further away from the charged object
• electric field line rules

  • go from positive to negative
  • at a right angle to the surface
• what happens when a charged object is placed in the electric field of another object?

  experiences a force

  • causes attraction/repulsion
  • caused by electric fields of charged object interacting with eachother
  • force of an object is linked to the strength of electric field it is in
• what happens when you increase the distance between charged objects?

  the field strength decreases - forces between them gets smaller
• how are sparks caused?

  high enough potential difference between charged object + earth
• what does this high potential difference cause?

  a strong electric field between charged object and earthed object
• what does this strong electric field cause?

  electrons in the air particles to be removed - ionisation
• what is air normally?

  an insulator - much more conductive when ionised - current can flow through it (sparrk)
• what does too much static charge cause?

  sparks
• explain the cause of sparks

  • electric charge builds on object - p.d. between charged object and earth increases
  • large enough p.d. = electrons can jump across gap
  • also jump to an earthed conductor - charge travels through individual
  • occurs when gap is fairly small