Topic 11 - Static Electricity

• What can happen when insulating materials are rubbed together?

  They can become (statically) electrically charged.
• Why can insulators become electrically charged when rubbed together?

  ● Electrons are rubbed from one material onto the

  other

  ● The material gaining electrons becomes

  negatively charged

  ● The material losing electrons becomes equally

  positively charged
• What would happen when two electrically charged objects are brought close together?

  They exert a force on each other
• What happens when two identically charged objects are brought close together?

  They exert a repulsive force on each other and repel.
• What happens when two oppositely charged objects are brought close together?

  They exert an attractive force on each other and attract.
• Give an example of a non-contact force

  The repulsive or attractive force acting between two electrically charged objects.
• Why do we feel an electric shock?

  When an object builds up an electrostatic charge it needs to be earthed via a conductor

  Electrons flow to/from the earth to balance charge

  This can also occur if you touch a charged object whilst you are earthed

  If earthing occurs through a person/animal it causes an electric shock
• Why does lightning occur?

  ● Clouds can build up an electrostatic charge.

  ● When this charge becomes large enough, the clouds discharge via the air to the earth.

  ● This is known as lightning
• Why does a charged balloon stick to the wall?

  When a positively charged balloon is placed next to a wall the positive charges near the balloon get repelled to other parts of the wall. This leaves an area of the wall with a negative charge which attracts the positively charged balloon towards the wall, making the balloon stick.

  (The inverse occurs with a negatively charged balloon)
• How does earthing remove excess charge?

  It provides a path with a low resistance for the electrons to flow either from the device or towards the device to reduce the charge build up
• How does static electricity cause danger when fuelling cars?


  ● Static charge can build up due to the friction between the pipes and the fuel flow

  ● When the charge builds up, a spark may be discharged

  ● The spark could start a fire if it reacts with the flammable fuel

  ● This is resolved by earthing the vehicle and pump
• What is an electric field?

  a region around a charged particle or object within which a force would be exerted on other charged particles or objects.
• What direction do the field lines in an electric field always point?

  In the direction that a positive charge would move (experience a force) from north to south
• Describe the appearance of electric field lines in a parallel field

  Straight lines, which are parallel to each other and point from the positive plate to the negative plate. At the edges, the lines are partially curved.
• How can you use electric fields to explain static electricity?

  - The object that is statically charged will generate an electric field

  - The field attracts the electrons on other objects causing a flow of charge resulting in sparks