P2- Electricity

• What do straight lines in circuit diagrams represent?

  Wires connecting components
• How are components represented in circuit diagrams?

  Using symbols
• What does a closed switch indicate in a circuit?

  That the circuit is complete
• What does a diode do?

  Allows current to flow in one direction
• What is the purpose of a fuse in a circuit?

  To protect the circuit by melting if the current is too high
• What is an ammeter used for?

  To measure current
• What does an LDR do?

  Changes resistance with light intensity
• What is required for electric current to flow?

  A closed circuit
• How is electric current measured?

  In amperes (A)
• What is an electrical insulator?

  A material that does not allow electric currents to pass through
• Why do metals conduct electricity?

  Because they have free electrons that can move
• What is potential difference measured in?

  Volts (V)
• What does a voltmeter measure?

  The potential difference between two points in a circuit
• How is resistance defined?

  As a measure of how difficult it is for current to flow through a component
• What happens to current if the potential difference is increased?

  The current will increase
• What is a thermistor?

  A component where resistance changes with temperature
• How does an LDR behave in bright light?

  Its resistance decreases
• What is the formula for power?

  Power = potential difference x current
• What does Ohm's law state?

  Current is directly proportional to potential difference across a resistor
• What are the characteristics of series circuits?

  • All components are on the same line
  • The current is the same at all points
  • Total resistance is the sum of individual resistances
  • Total potential difference is the sum of individual voltages
• What are the characteristics of parallel circuits?

  • Components are connected on separate branches
  • If one component breaks, the rest still work
  • Total current is the sum of currents through each branch
  • Each branch has the same potential difference as the power supply
• What is the frequency of alternating current in the UK?

  50 Hz
• What is the voltage of UK mains electricity?

  230 V
• What is the purpose of the earth wire in a plug?

  To prevent electric shock by carrying current only if there is a fault
• What happens when the live wire and earth wire connect?

  The earth wire is no longer safe
• How is electrical charge measured?

  In coulombs (C)
• What causes a spark during a thunderstorm?

  A rapid transfer of charge due to potential difference
• What is an electric field?

  The region around a charged object where it exerts a force on other charges
• How does the strength of an electric field change with distance?

  The closer an object is to the charge, the stronger the electric field
• What happens to the resistance of a thermistor as temperature increases?

  The resistance decreases
• What is the relationship between charge and potential difference?

  A difference in charge creates a potential difference
• What is the effect of increasing temperature on resistance in a conductor?

  Usually increases resistance
• What is the role of a circuit breaker?

  To switch off the flow of current if it exceeds a certain value
• What is the purpose of a fuse?

  To break the circuit if the current is too high
• What is the difference between a fuse and a circuit breaker?

  A fuse melts and breaks the circuit, while a circuit breaker can be reset
• What is the function of step-up transformers in the national grid?

  To increase the potential difference for efficient transmission
• What is the function of step-down transformers in the national grid?

  To reduce the potential difference to a safer level for homes
• What is the role of power stations in electricity generation?

  To create an electric current at a high voltage
• What is the relationship between power, current, and resistance?

  Power = current x resistance
• What is the formula for energy transferred?

  Energy transferred = power x time