Circuits

• Atom

  Made up of protons, electrons and neutrons
• Protons and neutrons


  • Contained in the nucleus (positively charged)
  • Smaller electrons (negatively charged) orbiting outside the nucleus
• Each particle (proton, electron, neutron) has its own charge and its own mass
• Charging a polythene rod by rubbing with a cloth


  1. Friction causes electrons to be knocked off atoms in the cloth

  2. Electrons stick to atoms in the polythene rod

  3. Polythene rod gains a negative charge

  4. Cloth gains a positive charge
• Opposite charges


  Attract
• Same charges


  Repel
• Requirements for a working circuit

  • Cell or battery to provide energy
  • Wires to make a complete circuit
  • Components (e.g. bulb) to make useful energy transfers
• Series circuit


  All components in one loop connected by wires, only one route for current to flow
• Parallel circuit


  Components on separate branches, current can take different routes
• Electric current


  Charge flowing per second in a circuit (usually electrons)
• Voltage


  • Measure of the energy transferred by the electrons as they flow between two points in the circuit
  • How hard the electrons are being pushed by the cell
• Resistance


  Measure of how difficult it is for current to flow
• Ohm's law


  Current and voltage are directly proportional (V=IxR)
• Fuse breaking a circuit

  1. Fuse contains a piece of wire that melts when current is too high

  2. Melted wire breaks the circuit
• Fuse protects wiring and appliance if something goes wrong
• To measure current you would use an ammeter
• When electricity flows through wires they get hot
• A fuse is a piece of wire that melts when it gets too hot
• If you touch electrical equipment with wet hands you might get an electric shock