Lesson 1.1

• Static electricity


  Electricity at rest produced when there is an imbalance of electrical charges
• Electricity comes from the Greek word elektron which means amber
• Amber


  • Able to produce static electricity when rubbed with a cloth
• Benjamin Franklin


  Carried out famous experiments involving flying kites during thunderstorms
• JJ Thomson


  Discovered negatively charged particles known as electrons
• Ernest Rutherford


  Discovered positively charged particles known as protons
• Charges


  Measured in coulombs (C)
• Unlike charges


  Attract
• Like charges


  Repel
• There is no attractive force between a neutral object and a charged object
• Charge separation in a neutral sphere

  1. External charged sphere is placed near the neutral sphere

  2. Charge separation occurs
• Atoms


  Made up of electrons, protons, and neutrons
• Net charge


  Sum of the number of electrons and protons
• Charging by friction


  Electrons are transferred when objects are rubbed against one another
• Electrons are transferred from one material to another during charging by friction
• The material that becomes negatively charged during charging by friction is the one that attracts electrons more strongly (higher electronegativity)
• Rubbing a silk cloth against a glass rod

  • Glass rod becomes positively charged
  • Silk cloth becomes negatively charged
• Electron affinity


  Chemical property of an atom to attract electrons
• Triboelectric series


  Ranks materials based on their tendency to acquire charge
• Charging by conduction


  1. A charged object is touched to a conductor

  2. Charge separation occurs when a negatively charged rod is placed near the sphere

  3. Upon contact, some electrons move from the rod to the sphere

  4. Upon separation, both the rod and the sphere obtain a negative charge
• Charging by induction


  1. Charge separation occurs in a neutral conductor when a charged object is brought near it

  2. The side of the conductor closest to the charged object takes on the opposite charge

  3. The side farthest from the charged object takes on the same charge

  4. When the charged object is removed, the conductor remains charged
• The law of conservation of charge states that the algebraic sum of all the electric charges in any closed system is constant
• There are two types of charges: positive and negative
• Changes in charges are brought by the movement of negatively charged particles
• Like charges repel and unlike charges attract
• There are two methods of charging an object: charging by friction and charging by induction
• Charging by friction can happen when you rub two objects with unequal electronegativity. The object with higher electronegativity will be negatively charged and the other object with lower electronegativity will be positively charged.
• Charging by induction can happen due to induced charges. The charges in a conducting object can be rearranged with the presence of an external charged object.