Topic 11

• 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 transfer 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 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.
• 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

  ● 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 where an electric charge will

  experience a non-contact force.
• What direction do the field lines in an electric field

  point?

  In the direction that a positive charge

  would move (experience a force).
• 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.
• Which field is the stronger field?

  The field lines being closer together shows a stronger field
• 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