Topic 11 Static Electricity

• What is static electricity a property of?

  All matter
• What happens when a body has equal amounts of positive and negative charge?

  They cancel out, forming a neutral body
• What do like charges do?


  Repel each other
• What do opposite charges do?

  Attract each other
• Why do insulators not conduct electricity?

  Their electrons cannot flow throughout the material
• How do conductors differ from insulators in terms of electron flow?

  Conductors have delocalized electrons that can flow
• What occurs when two insulators are rubbed together?

  • They can be charged by friction
  • Electrons are transferred from one object to another
  • One object becomes positively charged, the other negatively charged
• Why do conductors remain neutral when rubbed together?

  Electrons flow in and out, cancelling out any charge effect
• What charge forms on an object that loses electrons?

  A positive static charge
• What charge forms on an object that gains electrons?

  A negative static charge
• What determines which object loses or gains electrons when rubbed together?

  The materials involved
• What happens during sparking due to static electricity?

  • Charge builds up on objects that are close but not touching
  • A spark occurs when charge jumps through the air
  • This balances out the charges
• What causes lightning?

  A massive spark jumps across to balance the charge difference between clouds and the Earth
• What is the force experienced by charged objects called?

  Electrostatic force
• How does the magnitude of charge affect the electrostatic force?

  Greater charge results in a greater force
• How does distance affect the electrostatic force between charged objects?

  Closer together results in a greater force
• What is the relationship between force and distance in electrostatics?

  Force is proportional to the inverse square of the distance
• What type of force is electrostatic force?

  It is a noncontact force
• How does a positively charged balloon interact with a wall?

  It attracts electrons in the wall, causing induction
• What happens to small pieces of paper when a charged comb is brought near?

  The comb induces an opposite charge in the paper, causing it to be picked up
• What is earthing in the context of static electricity?

  • It allows electrons to flow to the earth
  • Removes excess charge
  • Helps materials stay neutral
• How are insecticide sprays made more effective using static electricity?

  • Sprayed from aircraft and given a charge
  • Charged droplets repel each other
  • Ensures even spread and attraction to the earth
• What danger can occur if a spark forms while fuelling cars?

  It could ignite and cause a massive explosion
• How can static charge build up during the fuelling process?

  As fuel passes through a hose to the vehicle
• What is done to prevent sparks during fuelling?

  The hoses are earthed
• What is an electric field?

  The region where an electric charge experiences a force
• In which direction do electric fields point?

  Away from positive charges and towards negative charges
• How are electric field lines oriented in relation to charged surfaces?


  They point to charges at right angles to the surface
• How does the strength of a charge affect electric field lines?

  Stronger charges have more field lines present and a stronger force felt
• What type of electric field do parallel plates create?

  A uniform electric field