Electric Circuits and Currents

• Cell


  Stores chemical energy and transfers it to electrical energy when a circuit is connected
• Battery


  Two or more cells connected together
• The cell's chemical energy is used up pushing a current round a circuit
• Electric current


  A flow of microscopic particles called electrons flowing through wires and components
• Direction of current flow

  From the negative terminal to the positive terminal of a cell
• Simple electric circuit

  1. Cell

  2. Lamp

  3. Switch

  4. Wires

  
• When the switch is closed, the lamp lights up because there is a continuous path of metal for the electric current to flow around
• Circuit diagram


  Symbols used to represent components
• Circuit diagram symbols


  • Cell
  • Battery
  • Switch
  • Lamp
  • Motor
  • Ammeter
  • Voltmeter
  • Buzzer
  • Resistor
  • Variable resistor

  
• Series circuit


  Components connected end-to-end, one after the other, making a simple loop for the current to flow round
• Parallel circuit


  Components connected side by side, the current has a choice of routes
• If one bulb 'blows' in a series circuit, it breaks the whole circuit and all the bulbs go out
• If one bulb 'blows' in a parallel circuit, there is still a complete circuit to the other bulb so it stays alight
• Ammeter


  Measures electric current in amps (A), connected in series in the circuit
• In a series circuit


  Current is the same at all points in the circuit
• In a parallel circuit


  Current is shared between the components
• Voltage


  The 'electrical push' which the cell gives to the current, measured in volts (V)
• The bigger the voltage supplied by the cell, the bigger the current
• Voltmeter


  Measures voltage (potential difference), connected across the components
• In a series circuit


  Voltage is shared between the components
• In a parallel circuit


  Voltage is the same in all parts of the circuit
• direct current


  is the flow of electric charge in a curcuit in one direction
• Alternative Current


  flow of electric charge that periodically reverses direction.
• Conventional Current


  electric charge moves from positive side of the battery to the negative side
• Electron Current


  electric charge moves form negative side of the battery to the positive side
• Ohm's Law


  states that the current (I) through a given conductor is directly proportional to the potential difference V between its end points