PHYSICS 2 3RD QUARTER

• Electric charge


  Objects become electrically charged either by gaining or losing electrons
• Amber


  • Translucent yellowish resin that attracts nearby objects when rubbed with a piece of cloth
• Queen Elizabeth I of England found out that many other substances possess the same ability as that of amber when rubbed against other substances
• Electrics


  Substances that possess the ability to attract small pieces of matter after being rubbed against another object
• Electricity


  The ability of amber to attract small pieces of matter
• Electrostatics


  The study of all phenomena associated with electric charges at rest

  
• Electric charge


  Represented as q, unit is coulomb (C)
• Conductivity


  The measure of the ease at which an electric charge moves through a material
• Conductors


  • Materials that allow the flow of charges through them
  • Have plenty of free electrons that can easily move in the materials
• Insulators


  • Materials that resist the flow of charges
• Semiconductors


  • Intermediate between conductors and insulators
  • Conductivity is low in its pure form
• Doping


  Atoms of different elements in very small amounts added to pure semiconductors to improve conductivity
• Superconductors


  • No resistance to the flow of charges below some critical temperatures
  • Only work at temperatures close to absolute zero
• The highest known critical temperature of a superconducting material is 203 K (-70°C): hydrogen sulfide
• Induced charges


  Neutral atom may gain or lose electrons
• Electron affinity


  A measure of the attraction of an atom to an electron
• Triboelectric series


  Arranged in the order of increasing electron affinity from top to bottom, one that is higher on the list will become positively charged
• Charging by conduction


  Requires physical contact between a charging body and a neutral body, neutral body becomes negatively charged when charged by a negatively charged body, neutral body becomes positively charged when charged by a positively charged body
• Charging by conduction without physical contact

  Polarization happens when negative charges on the neutral body are attracted toward the charging body if the latter is positive, the neutral body is then grounded either by touching it or using a wire
• Charges can neither be created nor destroyed, it only transferred from one body to another
• Coulomb's law


  The magnitude of the electrical force between two charged particles is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between them

  
• Electric field


  Space surrounding a charged body that causes any charged particle placed in it to experience an electric force

  
• Electric field lines

  • Start from positively charged particles and end on negatively charged particles, lines of force neither intersect nor break as they pass from one charge to another, the greater the number of lines of force, the stronger the electric field

  
• Electric field due to a point charge


  Electric field exists in the region of space around a charged object or a source charge, when another charged object enters this electric field, it experiences an electric force

  
• Electric flux


  Measure of the number of field lines passing through a surface, equal to the dot product of electric field and vector area
• Gauss' law


  Relates electric field, electric flux, and electric charge, the total electric flux through a surface is the total electric charge inside the surface divided by epsilon_0

  
• Electric potential


  Work must be done to move a charge in an electric field created by a point charge or a continuously distributed charge, electric potential at any point in an electric field E is electric potential energy per unit charge at that point

  
• Electric potential difference


  The work done by electric force in moving a unit positive test charge from point A to point B

  
• ELECTRIC CHARGE

  
  

  Objects become electrically charged either

  by gaining or losing electrons.
• QUEEN ELIZABETH I OF ENGLAND

  ★ Found out that many other substances

  possess the same ability as that of AMBER

  when rubbed against other substances.

  ★ Called these substance electrics and this

  the ability of amber electricity.
• Amber: translucent yellowish resin rubbed with a piece of cloth attracts nearby objects.
• ELECTROSTATICS

  ★ study all phenomena associated with

  electric charges at rest.
• ELECTRIC CHARGE

  ★ Electric charge represented as "q". Unit for

  charge is coulomb (C).
• FORMULA FOR ELECTRIC CHARGE:

  q = N e

  
  

  q = charge

  N = number of electrons

  e = charge of an electron (1.602 x 10 ^ -19 C)
• Metal (copper) is an example of good conductor
• Metalloid (silicon) is an example of semiconductor
• Non-metal (glass) is an example of insulator
• CONDUCTIVITY is the measure of the ease at which an

  electric charge moves through a material.
• CONDUCTORS are materials that allow the flow of charges

  through them.
• Conductors have plenty of free electrons that can easily flow in the materials.