Sensing

• What is current?

  The rate of flow of charge in a circuit
• How do you measure the current at a point in a circuit?

  Attach an ammeter in series
• Describe the current variations in series and parallel

  In series, the current is the same at all points

  In parallel, the current is split between the branches
• What is kirchoffs first law?

  An application of the conservation of charge

  'The total current entering a junction must be equal to the current leaving the junction'
• What equation is used to calculate the work done when a charge moves across a P.D

  Work done= charge × voltage
• What is power?

  The rate of transfer of energy
• What are 2 equations used to calculate power?

  P= energy transferred/time

  P= current × voltage
• What is the unit of power?

  Watts
• What is joule heating?

  When a resistance opposes the flow of charge, causing energy to be wasted as heat
• What is the opposite of resistance?

  Conductance
• What is conductance?

  A measure of how easily electrons can flow through a given material
• What are 2 equations for conductance?

  G= 1 / r

  G= current / voltage
• What is the equation for total resistance in series?

  $R=$$R_1 +$$R_2 +$$...$
• What is the equation for total resistance in parallel?

  $G=$$G_1+$$G_2+$$...$
• To find conductance in a circuit, find resistance and the convert using 1/r
• Why does resistance increase with temperature?

  With temperature increase, the ions in a metal gain more KE

  So they vibrate more, and then they collide more, making it harder for current to pass through
• What makes conductors good at conducting electricity?

  They have a large number of charge carriers (free electrons) that can carry a current
• How does a semiconductor work?


  The number of mobile charge carriers increase with a factor such as light or heat, meaning their ability to conduct electricity also increases
• What are 2 examples of semiconductors?

  LDRs

  Thermistors
• What is the electromotive force of a power supply?

  The EMF is the energy provided by the source per unit charge
• What is kirchoffs second law?

  The sum of all the voltages across a circuit must be equal to the EMF of the circuit
• What is internal resistance?

  The resistance in a power supply, due to the materials that it consists of