physics

• A magnet is any material or object that produces a magnetic field
• Common types of magnets include bar magnets, horseshoe magnets, and the Earth itself
• All magnets have two poles: a north pole and a south pole
• Magnetic fields are represented using field lines, which are effectively arrows drawn around the magnet from the north pole to the south pole
• Field lines show the direction and relative strength of the magnetic field

  • The more dense the field lines are (closer together), the stronger the magnetic field is in that area
• To represent a magnetic field with field lines:

  • Draw at least one straight line going into the south pole and coming out of the north pole
  • Draw a pair of slightly curved lines going into the south pole and a similar pair coming out of the north pole
  • Add looped lines that go all the way around from the north to the south pole
• Using a compass to find magnetic poles:

  • The needle of a compass is a tiny bar magnet that aligns with the magnetic field lines
  • The compass needle points towards the south pole of a magnet
  • Placing a compass near a magnet helps determine the north and south poles
• Interaction between two magnets:

  • North poles of two magnets repel each other
  • Field lines between repelling magnets show the interaction creating the repulsive force
  • Opposite poles (north and south) attract each other
  • All field lines go from north to south in attracting magnets
• Magnetic material: any object that can be influenced by a magnetic field and has the potential to become a magnet
• Not all magnetic materials are magnets; magnets produce a magnetic field while magnetic materials can be influenced by a magnetic field
• Common magnetic elements: nickel, cobalt, iron, and their alloys like steel
• Permanent magnets: produce their own magnetic field all the time
• Induced or temporary magnets: have a magnetic field temporarily when a piece of magnetic material is put into the field of a permanent magnet
• Force between permanent and induced magnets is always attractive
• Induced magnets lose their magnetism when removed from the magnetic field
• Magnetic materials like nickel and iron can be magnetically soft (lose magnetism quickly) or magnetically hard (lose magnetism slowly)
• One idea that many people get incorrect is the difference between heat and temperature. Heat energy or thermal energy is an energy store, it refers to the total amount of energy that can be stored in an object accounting for its size and particle movement. It is measured in Joules (J). Temperature is a measure of the kinetic energy of the particles in a substance in science it is measured in degrees Celsius (OC). The faster moving the particles are in a substance, the higher the temperature is. 
• The law of reflection states that the angle of incidence is equal to the angle of reflection.
• Refraction occurs when waves change speed because they are moving through a medium of a different density. 

  We can describe refraction using the sizes of the angle of incidence (𝑖) and the angle of refraction (𝑟).
• When light moves from a more dense medium to a less dense medium it bends away from the normal. 

  We can see that because the refracted ray is further from the normal than the incident ray is.

  The opposite happens when light moves from a less dense to more dense medium.