Physic

• Current flow


  The flow of electrons
• Benjamin Franklin assumed current went from positive to negative terminals


  1752
• This is called conventional current
• Conventional current flows from (+) to (-) polarity
• Electrons flow from (-) to (+) polarity
• Conductor


  • Allows current to flow
• Insulator


  • Prevents current from flowing
• Voltmeter


  • Measures voltage
• Ammeter


  • Measures current
• Voltage (U)


  Driving force for current
• Current (I)


  Rate of flow of charge
• Resistance (R)


  Opposition to current flow
• Ohm's law


  Relationship between voltage, current and resistance
• Magnet


  • Can exert a non-contact force
• Magnetic poles


  • North and South
• Magnetic field lines never cross each other
• Closer magnetic field lines

  Stronger the magnetic force
• Like magnetic poles


  Repel
• Unlike magnetic poles


  Attract
• Magnetic materials


  • Iron, cobalt, nickel
• Permanent magnet


  • Produces its own magnetic field
• Permanent magnet's magnetic field can't be turned on and off
• Temporary magnet


  • Made from material placed in a magnetic field
• Heating or striking a magnet can cause it to lose its magnetism
• Electromagnet


  • Has a wire coil around a magnetic core
• Increasing the number of coils


  Increases the magnetic field strength
• Increasing the current


  Increases the magnetic field strength
• Force


  A push or pull that causes an object to move, stop, or change direction
• Force properties


  • Direction
  • Magnitude
• Speed


  Distance / time
• Velocity


  Speed + direction
• Acceleration


  Change in velocity
• Once forces are balanced, terminal velocity is reached
• Typical parachutist can reach a terminal velocity of 240 km/h
• Relative speed


  Speed between two objects
• Moment


  Force x distance
• Clockwise moments are positive, anticlockwise moments are negative
• Pulley


  • Mechanical advantage is created by adding more wheels
• Inclined plane


  • A sloped surface
• Pressure


  Force per unit area