Resistance/current

• Field lines


  • Always have arrow-heads to show the direction of the force
  • Never cross over each other
• Gravitational force


  Always attractive
• What happens to the current in a circuit if the resistance increases while the voltage remains constant?

  The current decreases
• What role does voltage play in a complete circuit?

  Voltage provides the 'shove' that drives the current
• How does resistance affect the current in a circuit?

  Higher resistance results in lower current for the same voltage
• What happens to the current if the voltage is increased while keeping the resistance constant?

  The current increases
• What color wire in a UK plug is the live wire?

  Brown
• What color wire in a UK plug is the neutral wire?

  Blue
• What is the purpose of the Earth wire in a UK plug?

  It provides a low resistance path to Earth in case of a fault
• What happens if the metal outer casing of a device becomes live?

  The Earth wire causes a large surge current that melts the fuse wire
• What is the function of a fuse in an electrical circuit?

  A fuse prevents overheating and fire by breaking the circuit when the current is too high
• What are the typical ratings for fuses?

  3A, 5A, or 13A
• What are the key safety features of sockets in the lab?

  • Emergency stop that turns off all sockets
  • Switch for controlling power
  • Plastic gate that opens only when a plug is inserted
• What are the design features of a plug?

  • Fuse to protect against excess current
  • Earth pin and earth wire for safety
• What are the consequences of a fault in an electrical device?

  • Large current flows through the Earth wire
  • Fuse wire melts, isolating the device
  • Prevents overheating and electrical shock
• How does the Earth wire protect the user of an electrical device?

  • Provides a safe path for current if the device becomes live
  • Melts the fuse wire to break the circuit