ELECTRICITY

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  • ELECTRICITY
    • Symbols
      • Need to be able to draw and understand all of the symbols from the AQA Combined Science: Trilogy specification
    • Definitions
      • CHARGE - Unit of charge is the COULOMB (C). Equal to the charge of   6.24 x 10 24 electrons
      • CURRENT - The rate of flow of charge (C/s). One coulomb of charge flowing in one second is 1 AMPERE
      • VOLTAGE / P.D - The electric potential energy per coulomb of charge (J/C).
    • SERIES CIRCUIT
      • CURRENT remains the same throughout
      • VOLTAGE is shared across components
      • TOTAL RESISTANCE is equal to sum of resistance across all components
    • PARALLEL CIRCUIT
      • CURRENT is split between the junctions
      • VOLTAGE is the same across the components
      • 1/R TOTAL = 1/R of each resistor *NOT NEEDED FOR GCSE*
    • Domestic electricity
      • Runs on alternating current (a.c.) and had a P.D of 230 V at a frequency of 50 Hz (changes direction 50 times per second)
      • In a U.K. plug, the BROWN (LIVE) wire has a P.D. of 230 V and the BLUE (NEUTRAL) wire has a P.D. of 0 V. The EARTH (GREEN AND YELLOW) only carries the current if there is a fault
      • The National Grid
        • A system of cables and transformers linking power stations to consumers.
        • Step-up transformers are used to increase the potential difference  then step-down transformers are used to decrease, to a much lower value, the potential difference for domestic use.
    • EQUATIONS
      • P = IV (Power (W) = Current (A) x Voltage (V)
      • P = I2R (Power (W) = Current squared (A) x Resistance (ohms)
      • E = Pt (Energy transferred (J) = Power (W) x Time (s)
      • E = QV (Energy transferred (J) = Charge (C) x Voltage (V)

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