electricty

• Series circuit


  A circuit with no branches, where the current can only flow in one path around the circuit
• Electric current


  The flow of electrical charge around a circuit
• Electric current


  • Flows from the negative end of the cell to the positive end
  • Electrons carry energy from the cell and pass it to the components in the circuit
  • Electrons return to the positive end of the cell with less energy
• Conventional current


  The current is drawn as flowing from the positive end of the cell to the negative end, even though we now know this is incorrect
• The unit of electric current is the Ampere (A)
• Ammeter


  A device used to measure the electric current in a circuit
• In a series circuit, the current is the same all the way around the circuit
• Current is never used up in a circuit
• Parallel circuit


  A circuit that contains branches, where the current splits and passes through multiple paths
• Current flow in a parallel circuit

  1. Current splits and passes through multiple branches

  2. Current in each branch adds up to the total current leaving the cell
• Current is measured using an ammeter placed in the circuit
• In a series circuit, the current is the same all the way around
• In a parallel circuit

  The current in the branches adds up to the total current leaving the cell
• potential difference is a measure of work (enegy transferred) to the lamp by each coloumb of charge thatb passes through it
• Potential difference


  The energy transferred per unit of charge moving through a circuit
• Measuring potential difference


  1. Use a voltmeter

  2. Connect voltmeter across the component
• Potential difference across a component


  Indicates the energy transferred to that component
• Potential difference of 1 volt = 1 Joule of energy transferred per Coulomb of charge
• Potential difference across a cell


  Indicates the total energy transferred in the circuit
• Connecting lamps in series

  • Shares the total energy transfer between the lamps
  • Lamps become dimmer
• Lamps in series circuit

  • Can have different potential differences
  • Total potential difference across lamps equals potential difference of cell
• Brighter lamp has higher potential difference, transferring more energy
• Potential difference


  Tells us about energy transfers taking place in a circuit. One volt of potential difference means one Joule of energy is transferred for each Coulomb of charge moving through the circuit.
• In a series circuit, potential difference is split between components.
• Parallel circuit


  Has branches, and some of the current passes through each branch.
• In a parallel circuit, the potential difference across each component is the same.
• Measuring potential difference in a parallel circuit

  1. Use a voltmeter across the cell

  2. Use a voltmeter across the branches
• Potential difference measurements in a parallel circuit

  • Cell potential difference is 6 volts
  • Top lamp potential difference is 6 volts
  • Bottom lamp potential difference is 6 volts
• When components are connected in parallel


  The potential difference across each component is the same
• Calculating potential difference in a parallel circuit

  • Potential difference across top lamp is 12 volts
  • Potential difference across bottom lamp is 9 volts (2 volts + 7 volts)
• Battery


  Two or more cells connected together
• Cells in a battery must be connected in the same direction
• Potential difference of a battery

  The sum of the potential differences of the individual cells
• Battery with two 9V cells

  • Total potential difference is 18V
• Calculating potential difference of a battery

  Multiply the potential difference of each cell by the number of cells connected in the same direction
• Battery with three 9V cells

  • Total potential difference is 27V
• Battery with two 9V cells connected in opposite directions


  • Total potential difference is 0V
• Battery with three 9V cells, two in the same direction and one in the opposite direction


  • Total potential difference is 9V
• You can find more questions on determining the potential difference of batteries in the revision workbook
• Resistance


  The potential difference required to drive a current through a component