Current Electricity 7J

• Plastics are good insulators
• Metals are good conductors of electricity
• Requirements for current to flow in a circuit

  • A complete circuit with no gaps
  • A cell or power supply
• Electricity is a flow of charges
• Current


  The amount of electricity flowing in the circuit, measured in amps (A)
• Measuring electricity

  • Current is measured using an ammeter connected in series
  • Voltage is measured using a voltmeter connected in parallel
• Electricity can flow through conductors but not through insulators
• Voltage


  Provides the "push" and energy, measured in volts (V)
• Factors affecting resistance

  • High resistance = hard for electricity to flow = small current
  • Low resistance = easy for electricity to flow = large current
  • Thin wires and resistors have high resistances
  • Thick wires have low resistances
• One model for a circuit is a central heating system where the boiler and pump represent the cell, the pipes represent the wires
• Resistance


  A way of saying how easy or difficult it is for electricity to flow
• Fuses are used in plugs to melt if the current gets too high, with a specific rating to show what current they can carry without melting
• Wiring in houses is designed to be safe
• Cables have three color-coded inner wires: live (brown), neutral (blue), and earth (green and yellow)
• Electricity can be dangerous if not used properly, causing fires, burns, shocks, etc.
• Circuit breakers cut off the current if it gets too high, protecting the ring mains in buildings
• Voltage is provided by the cell, battery or power pack
• Sources of voltage

  • Cell
  • Battery
  • Power pack
• Voltage


  What helps to push the charge around the circuit
• Elastic materials


  If a force is applied to a spring it changes shape, but when the force is released, the spring returns to its original shape. This is called.…….
• Plastic materials


  If a force is applied, the material changes shape and when the force is released, the material keeps its new shape and does not return to its original shape. This is called.…..
• Components of a circuit

  • Cell
  • Open switch
  • Closed switch
  • Battery
  • Bulb
  • Ammeter
  • Resistor
  • Voltmeter
  • Diode
  • Inductor
  • Thermistor
• Discovering electricity/Current

  • ammeter
  • amp (A)
  • battery
  • cel
  • component
  • current
  • filament
  • power pack
• Mass


  The amount of matter that an object contains
• Mass is measured in kilograms
• Weight


  A measure of the force of gravity acting on an object
• Weight is measured in Newtons
• This is a variable resisitor, it is a component that can be changed to change the resistance of the circuit

  
• This is a fixed resistor. It is a component that limits the current flowing through it.

  
• This is a thermistor