Physics

• Current is the rate of flow of charge through a circuit, measured in amps (A)
• An electron is a tiny negative charged particle
• An atom contains electrons which can flow.
• Voltage is the force that pushes electrons through a circuit. It is measured in volts.
• Resistance is the opposition to the flow of charge in a circuit.
• Potential difference is the work done per unit charge, measured in volts.
• Current only flows if there is a complete circuit. If there is a break in the circuit, the current stops. There needs to be a source of voltage to make the circuit complete, and a low enough resistance to allow the current to flow.
• A series circuit is a circuit in which the current is the same in all branches.
• Parallel circuits: A circuit in which the current is split between two or more branches.
• Resistance is measured in ohms (Ω) and is a measure of how difficult it is for current to flow through a component.
• An increase in cells makes the charge flow faster as there is more energy.
• An increase in bulbs or resistance makes the charge flow slower.
• Current is constant all round a series circuit.
• In a parallel circuit, most of the current flows through the path with the least resistance.
• Current is not used up by the components.
• To predict the size of current in a series circuit, know that is the same everywhere.
• To predict the current in a parallel circuit, you can use Ohm's Law. V = IR.
• Resistance is an obstruction to the current.
• Resistance converts the electrical energy to heat.
• Fuses are used to protect electrical circuits from overheating and melting.
• If too much current flows, the wires can melt.
• The correct rating of fuse must be used because the fuse must be able to withstand the current that the circuit is designed to carry. The fuse should be slightly higher than the current rating.
• For things such as kettles and underfloor heating, you want a higher resistance, as you want heat.
• Neutral wire = Blue and on the left.
• Live wire = Brown and on the right.
• Earth wire = Green + Yellow and at the top.
• Every branch in the parallel circuit has the full potential difference across it. The total potential difference across the circuit is the sum of the potential differences across each branch.
• A bulb circuit symbol

  
• An ammeter circuit symbol

  
• A voltmeter circuit symbol

  
• A switch circuit symbol

  
• A cell circuit symbol

  
• A battery circuit symbol

  
• A resistor circuit symbol

  
• A variable resistor circuit symbol

  
• A series circuit


  Correct definition: An electric circuit with only one path through which charge can flow.

  
  

  Simple definition: all components are on one loop.

  
• A parellel circuit


  Correct definition:: A circuit that contains more than one path for current flow.

  
  

  Simple definition: the components are on separate branches, or loops.

  
• Ohm's law equation


  V=IR

  
  

  This can be used to calculate the resistance in a circuit, when the voltage and current are known.

  
• Electric current definition


  The rate of flow of charge.
• The charge carriers in an electric circuit

  Electrons