Physics P2 Electricity

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  • Electricity
    • Static Electricity
      • Some insulating materials become electrically charged when they are rubbed together.
      • Charges that are the same repel while opposite charges attract.
      • When you rub 2 insulators together they become electrically charged
        • This only works for insulated objects as metals arer easily earthed.
      • When the materials are rubbed against each other:
        • The material that gains electrons becomes negatively charged
        • The material that loses electrons  becomes positely charged
          • Both materials gain an equal amount of charge, but are opposite.
            • The material that gains electrons becomes negatively charged
        • Negetively charged particles called electrons move from one material to the other.
      • Two charged objects will repel if they have the same charge
      • If one object is charged you can check by seeing if small uncharged objects are attracted
    • Current and Voltage
      • For a curcuit to work there must be a  complete circuit and no short circuits
      • Series circuits are circuits where all the components are attached by the same wire-and the current is the same
      • Parallel circuits are circuits where electrons can go multiple ways in a complete circuit-so it is shared.
      • Electric current is a flow of electric charge and is measured in amperes which is measured by an ammeter
      • Calculating current I=Q/t (I is current in amps, Q is charge in coulombs and t is time in seconds)
      • Potential difference, voltage, is needed to make a current go through it. It is measured in volts and measured with a voltmeter.
      • Calculating charge V=W/Q (V is voltage in volts, W is work done in joules and Q is charge in coulombs)
      • A cell produces a voltage of 1.5V in a current and when more is connected, the more potential difference.
    • Resistance
      • Resistance is measured in Ohms. The total resistance is all the componants resistances added together.
      • There is a resistance to the flow of electric current through most conducters
      • The resistance of the wire increases as the length of the wire increases and the thickness of the wire decreases.
      • An electric current flows when electrons move through a conductor and when the electrons collide with ions it is more difficult for current to flow and causes resistance.
        • The resistance of a long wire is big because the electrons collide with ions more often.
        • The resistance is higher in a thin wire because there are fewer electrons to carry the current.
      • The equation for current is V=I*R (V is voltage in volts, I is current in amps and R is resistance in Ohms)
      • A current flowing through a resistor at a constant temperature is directly proportional to the p.d across it.
      • A filament lamp is a type of light bulb and when current goes through it it creates an S shape on the graph.
      • A diode has high resistance in 1 direction which means the graph is at zero until enough current flows through it.
    • Household Electricity
      • Direct current is where the current can only flow in one direction eg. batteries and cells
      • Alternating current is where the current is constantly changing direction and a frequency of 50Hz.
      • The blue wire is neutral, the brown wire is live and green/yellow is earth
      • The plug
        • There is a fuse
        • The pins are made from brass to conduct electricity
        • The fuse can break at high current
        • The case is made from rubber.
        • A cable grip holds the wires down.
      • Fuses protect electrical appliances by blowing if too much current passes through them. It contains a wire which melts easily.
        • Fuses are usually 3A, 5A and 13A
        • Circuit breakers protect an electrical appliance by switching off the appliance if too much current is supplied
      • Earthing protects appliances by connecting to metal areas and any current on the wire will be sent to the fuse.
    • Current, Charge and Power
      • Electric appliances are changed in order to make them more efficient as it makes the appliance more useful
      • Power is a representation of how much energy is transferred in a given time.
      • P=E/t (P is the power in watts, E is the energy transferred in joules and t is time in seconds.)
      • E=V*Q (E is energy transferred in joules, V is voltage in volts and Q is charge in Coulombs)


Miss KHP

Great revision tool! I'd recommend people have a look! Covers the 5 core topics in an easy to read format. I like how the topics are split into colour categories, which makes it easy to read and remember!  

Test yourself once you have done to check your progress

Former Member

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