p4

• Resistance


  A measure of how difficult it is for electric current to flow through a material
• Ohm (Ω)


  The unit of resistance
• Ohm's Law


  The formula that relates voltage, current, and resistance
• Series circuit


  • Current is the same through all components
  • Voltage drops across each component are different
• Parallel circuit


  • Voltage is the same across all components
  • Currents through each component are different
• Finding total resistance in series circuit


  Add the individual resistances
• Finding total resistance in parallel circuit

  1/Total Resistance = 1/R1 + 1/R2 + 1/R3 + ...
• An electromagnet is a type of magnet that can be turned on and off by controlling the flow of electric current through a wire.
• Voltage = Current x Resistance 
• Current = Voltage ÷ Resistance 
• Resistance = Voltage ÷ Current
• Unlike permanent magnets, which are always magnetic, electromagnets are temporary magnets that become magnetic only when an electric current flows through them. 
• The current in parallel circuits is different
• Series circuit


  If the ammeter reading is 0.5A across one resistor, the reading across another resistor in the circuit is 0.5A
• An ammeter be connected in series when measuring current in a circuit because objects in series experience the same current
• Parallel circuit


  If a voltmeter reads 9V across one branch, the voltmeter reading be across a different branch in the same circuit is 9V
• In a series circuit, not every component receives the full supply voltage from the battery
• In a parallel circuit with three branches, if the total current is 3A and the current in one branch is 1A

  The total current in the other two branches combined is 2A
• You connect a voltmeter to measure the voltage drop across a light bulb in parallel
• If three identical resistors are connected in a series circuit with a 12V battery

  The voltage drop across each resistor is 4v
• Household wiring is usually connected in a parallel circuit design instead of series because if one component breaks, the circuit can still function
• If the ammeter reading in a parallel circuit is 4A before the splits, and 2A in one branch after the split

  The ammeter reading be in the other branch would be 2A
• In a parallel circuit, adding more components on new branches will not cause the voltage across existing branches to decrease
• Label it (don't do the last line)

  A) Cell

  B) Battery

  C) Open Switch

  D) Closed switch

  E) Bulb

  F) Resistor

  G) Variable resistor

  H) Voltmeter

  I) Ammeter

  J) Fuse

  
• When a piece of iron is placed next to a magnetised. This is called induced magnetism or temporary magnetism.
• Steel, iron and compasses can be used to plot a magnetic field
• Compasses usually align with Earth's magnetic south pole
• Earth’s magnetic field is created by the liquid iron core solidifying, stirring up the surrounding iron and causing strong electrical currents.
• The magnetic field cause the needle of a compass as it is magnetic, pointing to Earth’s magnetic North, which is slightly different from true North, although they are roughly the same.
• To use a compass, you rotate the compass until the needle lines up with the ‘N.’ This tells you where North, is, and from there you can work out the other directions from there. You can also find which way you need to go if you match it with a map.
• A magnet has two poles - north (N) and south (S). The opposite ends attract each other while like poles repel each other.
• An electromagnet is often used for picking up scrap metal
• Permanent magnets are favoured for fridge magnets
• When electricity flows through a wire, it creates a magnetic field around that wire.
• Electromagnets are made by passing an electric current through a wire coil around a soft iron core. When the current stops flowing, the magnet loses its strength.
• If we pass a current through a solenoid (a long coil), then the magnetic field inside becomes very strong.
• An open switch means it is off
• A closed switch means it is on
• Voltmeters are connected in parallel
• Ammeters are connected in series