CP9

• What is a ‘free’ electron?

  An electron removed from its atom
• In which direction does conventional current flow?

  From positive to negative terminal
• How do you draw a circuit with two batteries and three bulbs in series?

  • Connect batteries in series
  • Connect bulbs in series
  • Ensure all components are connected in a single path
• How do you draw a circuit with two batteries and three bulbs in parallel?

  • Connect batteries in parallel
  • Connect bulbs in parallel
  • Ensure each bulb has its own path to the batteries
• What is current measured in?

  Amps (A)
• How is current measured?

  With an ammeter
• What happens to current at a junction?

  Current in is equal to current out
• What is the unit of potential difference?

  Volts (V)
• How is potential difference measured?

  With a voltmeter
• What is the reading on meter A?

  20mA
• What is the reading on meter B?

  0.75V
• What is the unit of electric charge?

  Coulombs (C)
• What is the equation for charge?

  Charge = current x time
• What is the unit of current?

  Amps (A)
• What is 1 Volt equal to?

  1 joule per coulomb (J/C)
• What is the equation for energy transferred?

  Energy transferred = charge moved x potential difference
• How is an ammeter connected to measure current?

  In series with the component
• What happens to the total current in a circuit?

  It is conserved around the circuit
• What is the unit of resistance?

  Ohms (Ω)
• What is true about current at a junction in a parallel circuit?

  Current entering equals total leaving
• What is the equation for resistance?

  Potential difference = current x resistance
• What charge do electrons have?

  Negatively charged
• Why can electrons in metals be easily removed?

  They are weakly attracted to the nucleus
• What pushes free electrons around a circuit?

  The voltage from the battery
• In which direction do electrons move in a circuit?

  Towards the positive terminal of the battery
• What is conventional current?

  It flows from positive to negative
• Calculate the resistance in a circuit with a potential difference of 6V and a current of 0.3A.

  30 Ω
• What is used to show components in a circuit?

  Circuit diagrams
• What component can be used to change the current in a circuit?

  A variable resistor
• What causes electrons to flow through a component?

  A potential difference across the component
• What is the unit of potential difference?

  Volts (V)
• Describe the resistance of a filament lamp.

  Resistance increases with potential difference and current
• How is a voltmeter connected to measure potential difference?

  In parallel with the component
• Describe the resistance of a diode.

  High resistance in one direction, low in the other
• What is true about potential difference in a parallel circuit?

  It is the same across each branch
• Describe the resistance of an LDR.

  Resistance decreases as light intensity increases
• What happens to potential difference across multiple components in a branch?

  It adds up to the total supplied
• What is charge measured in?

  Coulombs (C)
• Describe the resistance of a thermistor.

  Resistance decreases as temperature increases
• What does one Coulomb represent in terms of current?

  Charge passing in 1 amp for 1 second