Electricity

• What is the definition of electric current?

  Electric current is a flow of electrical charge.
• What is required for electric current to flow in a circuit?

  A complete (closed) circuit and a source of potential difference are required.
• What is the unit of current?

  The unit of current is the ampere, A.
• How does current behave in a single closed loop circuit?

  The current has the same value everywhere in the circuit.
• What is potential difference also known as?

  Potential difference is also known as voltage.
• What is the unit of potential difference?

  The unit of potential difference is the volt, V.
• What does resistance do in a circuit?

  Resistance slows the flow of electrical charge.
• What is the unit of resistance?

  The unit of resistance is the ohm, Ω.
• How does current depend on potential difference and resistance?

  The current flowing through a component depends on the potential difference across it and the resistance of the component.
• What is the formula for charge flow in a circuit?

  The formula is $Q =$$It$, where Q is charge in coulombs, I is current in amperes, and t is time in seconds.
• What happens to charge flow when a larger current flows?

  More charge passes around the circuit when a larger current flows.
• What are the steps to draw a circuit diagram correctly?

  • Use straight lines for wires.
  • Ensure the circuit is closed.
  • Include correct symbols for components like batteries and switches.
• How much charge is transferred to a cell if a battery charger passes a current of 2.0 A for 2.5 hours?

  The charge transferred is $Q =$$2.0 \times (2.5 \times 60 \times 60) =$$18,000 \text{ C}$.
• If a laptop charger passes a current of 8 A, how long must it be connected to transfer 28,800 C of charge?

  It must be connected for 60 minutes.
• What is the formula linking potential difference and current?

  The formula is $V =$$IR$, where V is potential difference, I is current, and R is resistance.
• If a 40 Ω resistor has a potential difference of 6.0 V across it, what is the current through the resistor?

  The current is $I =$$\frac{6.0}{40} =$$0.15 \text{ A}$.
• What factors can affect the resistance of a circuit?

  • The arrangement of components (series or parallel).
  • The length of the wire used.
  • The diameter of the wire.
  • The material of the wire.
• What does an ammeter measure?

  An ammeter measures the current flowing through a circuit.
• What does a voltmeter measure?

  A voltmeter measures the potential difference across a component.
• How should an ammeter be connected in a circuit?

  An ammeter must always be placed in series with the component being investigated.
• How should a voltmeter be connected in a circuit?

  A voltmeter must always be placed in parallel around the component being investigated.
• What is the relationship between resistance and wire length in a circuit?

  Resistance is directly proportional to the length of the wire.
• What happens to the resistance of a filament lamp as the current increases?

  The resistance increases as the current increases due to heating.
• How does the resistance of a diode change with current direction?

  The resistance of a diode is low in one direction and very high in the reverse direction.
• What are the characteristics of ohmic conductors?

  • Resistance remains constant.
  • Current is directly proportional to potential difference at constant temperature.
• What are the characteristics of non-ohmic conductors?

  • Resistance changes with current.
  • Examples include filament lamps and diodes.
• What does the term 'I-V characteristic' refer to?

  'I-V characteristic' refers to a graph showing how current changes as potential difference varies.
• How do you determine the resistance from an I-V characteristic graph?

  You can calculate resistance using $R =$$\frac{V}{I}$ at any point on the graph.
• What are the applications of LDRs?

  • Automatic night lights
  • Outdoor lighting
  • Burglar detectors
• What are the applications of thermistors?

  • Car engine temperature sensors
  • Electronic thermostats
• How does a sensing circuit work with a thermistor?

  As temperature increases, the thermistor's resistance decreases, allowing more current to flow.
• What happens to the potential difference across components in a parallel circuit?

  The potential difference across each component is the same in a parallel circuit.
• What happens to the current in a parallel circuit?

  The total current is the sum of the currents through each component.
• What are the key differences between series and parallel circuits?

  • Series: Current is the same, potential difference is shared, total resistance adds up.
  • Parallel: Current is divided, potential difference is the same, total resistance decreases.
• What happens if you disconnect a component in a series circuit?

  If you disconnect any component, the circuit is broken and all components stop working.
• How does the total potential difference behave in a series circuit?

  The total potential difference is the sum of the potential differences across each component.
• How does the total resistance behave in a series circuit?

  The total resistance is the sum of the resistances of each component.
• What is the effect of adding more cells in series?

  Adding more cells in series increases the total potential difference.
• What is the main advantage of parallel circuits over series circuits?

  Parallel circuits allow components to operate independently and continue functioning if one component fails.
• What is the main disadvantage of series circuits?

  The main disadvantage is that if one component fails, the entire circuit stops working.