static electricity

• how does an object become negatively charged?

  • Gains electrons
  • Looses protons
• What happens when 2 charged particles are close together?

  They exert a force on eachother

  • attractive force between opposite charges
  • repulsive force between same charges
• What is charging by friction?

  • When 2 insulating materials are rubbed against each other to become electrically charged
  • The charge remains on the insulator as it cannot immediatly flow away
  • One object gains a positive net charge
  • One gains a negative net charge
• How do electrons move when charging by friction occurs?

  • Electrons are transferred from one object to another
  • The object which looses electrons becomes positive
• what is static electricity?

  • Caused by a build up of stationary charge on a surface
  • occurs in insulators
• what causes a spark/shock

  • The build up of electrostatic charges
• when does a spark occur between 2 objects?

  • There is a large potential difference between the objects which causes a current to flow through them
• what are the dangers of sparking

  • electrocution
  • ignition of a fire
• how is lightening caused?

  • Ice crystals in clouds rub against each other causing a movement of electrons between them
  • The top of the cloud becomes positively charged and the bottom is negatively charged
  • The electrons on the ground are repelled by the charge in the cloud, causign them to beocme positive
  • The PD between the cloud and the ground becomes increasingly large
  • Eventually the cloud discharged a spark as the negative charges jump to meet the positive charges on the ground
• What controls the strength of an electric field?

  • The field is strongest when its closer to the charged object
• what happens when an objec tenters an electric field

  • it is either attracted or repulsed
• how is a positive electric field shown

  field lines point away from centre
• how is a negative field shown

  point towards the centre