science 3

• Explain the operation of a simple electric motor and generator
• Most Essential Learning Competencies (MELCs)

  • How do we benefit from generators and motors?
• Electricity


  What is electricity?
• Magnetism

  What is magnetism?
• Can they coexist?


  How can their coexistence benefit us?
• What would happen when you put a compass near a wire with electric current?
• What would happen when you repeatedly put in and out a magnet from a coil of wire?
• Static electricity


  Imbalance of accumulated charges
• Current electricity


  More known form of electricity; imbalance of distribution of moving charge/s
• First observed by Greeks. Amber + wool, grass rubbed attraction of particles.
• Static electricity


  • https://www.scienceworld.ca/resource/static-electricity/
• Current electricity


  • https://www.youtube.com/watch?v=kYwNj9uauJ4
• Observed by Turkish people in District of Magnesia in Asia Minor (now Turkey). Lodestone (magnetite) – attracts pieces of iron.
• For 2,000 years before 1800's, thought to be as separate phenomena.
• Compass needle deflects when electric current flows nearby.
• Application: Motor (later discussion)
• Magnetism is due to changes in motion of electrons that result to magnetic field
• Ampere's Law

  • https://phys.org/news/2015-12-earth-layers.html
  • https://fractory.com/magnetic-metals-non-magnetic-metals-with-examples/
• Magnetic field (B)

  It is the region that surrounds a magnet which can be a permanent magnet or a current-carrying conductor. Permanent magnet has curved magnetic field lines that move from north to south. Current-carrying conductor has magnetic field in concentric circles surrounding the circumference of the conductor. The closer from conductor, the higher the B. The farther from conductor, the lower the B. B may be moving clockwise or counterclockwise.
• Circuit-compass (electricity-magnetism) interaction may be increased by: 1. Using solenoid instead of just straight wire, 2. Transforming a simple solenoid into an electromagnet (added with iron core), 3. Increase in electric current. Change in direction of the current changes the direction of the magnetic field.
• Magnetic field (B)


  Unit: Tesla (T) = N/(A*m). It is a vector quantity, having both quantity and direction. For the direction of magnetic field, wait for later discussion on Right Hand Rule.
• Magnetic force (F)


  It can be attraction (moving closer together) or repulsion (moving away from each other). It is always 90 degrees from magnetic field. See the Right Hand Rule.
• Magnetic force


  General Formula: F = /qVB/sinɵ, F = C(m/s)T(sin˚), F = ILBsinɵ, F = C(m/s)T(sin˚)
• Right Hand Rule
• Motor

  Converts/Transforms Electrical Energy to Mechanical Energy
• Rectangular coil rotates due to combined upward and downward magnetic forces being provided by the interaction of the forward and backward motion of current (V) and the north pole to south pole movement of the magnetic field (B)
• Application of Right Hand Rule
• Motor

  • https://www.youtube.com/watch?v=CWulQ1ZSE3c
• Remove any source of electricity, put a magnet inward a solenoid, put a magnet away from a solenoid, use galvanometer or ammeter to detect presence of current electricity/electric current.
• By simply keeping magnet at rest inside or outside the solenoid, no electricity can be induced. Electricity is produced by changing the position of magnet relative to the solenoid.
• Changing the presence of magnetic field induces current in a conductor
• Induced Electromotive Force (Ɛ)

  Causes electrons to move due to electromagnetic induction
• Induced Current (I)


  Flow of electron due to electromotive force
• Magnetic flux (Φ)


  BcosθA, where B is the magnetic field intensity (Tesla, T), A is the area pass through by magnetic field intensity (m^2), and θ is the angle of magnetic field lines from the normal (degrees, ⁰)
• Change in Φ = induced EMF = induced current
• How to change the magnetic flux (Φ)

  1. Change B, 2. Change θ, 3. Change A
• Faraday's Law


  Induced EMF depends on change in Φ. Ɛ = -N (ΔΦ/Δt), where "-" indicates the direction or polarity
• Lenz's Law


  The direction of any EM induction effect is to the direction opposing the cause of the effect; indicates resistance to change
• Generator


  Converts/Transforms Mechanical Energy to Electrical Energy
• Generator


  • https://www.youtube.com/watch?v=Ylgb8FFMgd4