topic 10 - electricity and circuits

    Cards (17)

    • current
      • flow of electric charges
      • measured in amps (A)
      • has the same value at every point in a single closed loop
    • current equation
      current = charge / time
    • symbol equation for charge
      Q = I x T
    • electrical insulators
      • materials that don't allow electric current to pass through them
      • e.g. plastic and glass
    • electrical conductors
      • has lots of free charges (electrons in metals) that are able to move
      • current going through metal is the movement of these electrons through the metal
    • potential difference
      • measured in volts
      • energy transferred per unit charge in a circuit.
      • It tells us how much energy each coulomb of charge gains or loses as it moves between two points.
    • coulomb
      the unit of electric charge. It tells us how much electric charge is flowing in a circuit.
      quantity - like a litre of water, coulomb measures electrical charge
    • p.d. / voltage equation
      v = energy transferred / charge
    • potential difference of one volt = 1 joule of energy being used by a coulomb of charge when it flows between 2 points on a circuit
    • ammeter
      • measures flow of current that passes through it
      • have to be connected in series (in the same loop of the circuit) of the component you're measuring
    • voltmeters
      • measures pd between 2 points in a circuit
      • must always be connected in parallel (on seperat branch of circuit) to points being measured
    • energy, voltage and charge equation
      E = QV
    • Why do resistors become warm
      • collisions between electrons and lattice
      • Lattice moves more causing more heat
    • 3 wire plug
      • Brown- live wire. Carries current into appliance
      • blue- neutral wire. Completes circuit by carrying current away, close to 0V
      • Green/yellow - safety feature, prevents appliance from becoming live, only connected to metal casing, only carries current if there is a fault
    • Fuse
      • thin wire that melts and breaks circuit if current = too high
      • protects appliance, prevents fires
      • fuse melts and stops flow of electricity
    • Purpose of earth wire
      • prevents metal case from becoming live
      • By carrying current to the ground
    • why would a kettle need an earth wire
      • case = metal, could become live if live wire touches it
      • earth wire provides low resistance path for current to flow to ground
      • causes fuse to blow and break circuit