PT11, static electricity

• 1. What can happen when insulating materials are rubbed together?

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

  - Electrons transfer from one material onto the other

  - The material gaining electrons become negatively charged

  - The material losing electrons become equally positively charged
• 3. What can happen when two electrically charged objects are brought close together?

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

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

  They exert an attractive force on each other and attract
• 6. Why do we feel 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 the 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
• 7. Why does lightening 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
• 8. 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 a positively charged balloon towards the wall making the balloon stick. (This inverse occurs with a negatively charged balloon)
• 9. 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 a device to reduce the charge build up
• 10. How does static electricity cause danger when fuelling a car?


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

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

  - The spark could start a fire if ur reacts with the flammable fuel

  - This is resolved by earthing the vehicle and pump
• 11. What is an electric field?

  A region where an electric charge will experience a non-contact force
• 12. What direction do the field lines in an electric field point?

  In the direction that a positive charge would move (experience a force)
• 13. 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
• 14. How can you tell if a field is strong?

  The field lines will be closer together
• 15. How can you use electric fields to explain static electricity?

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

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