Electricity End of unit (1)
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Questions and Answers

What is the relationship between charge flow, current, and time as given by the equation?

  • Charge flow = Current - Time
  • Charge flow = Current + Time
  • Charge flow = Time × Current
  • Charge flow = Current × Time (correct)

    • In a series circuit, what is true about the current through each component?

  • The same current flows through each component. (correct)
  • The current is different through each component.
  • There is no current flowing.
  • The current fluctuates depending on the component.

    • What happens to the total resistance when resistors are added in series?

  • It remains constant.
  • It decreases.
  • It increases. (correct)
  • It becomes equal to the smallest resistor.

    • Which statement about a diode is true?

    <p>It only allows current to flow in one direction.</p> Signup and view all the answers

    What happens to the total resistance when resistors are added in series?

    <p>Total resistance increases.</p> Signup and view all the answers

    How is power calculated in a circuit?

    <p>Power = Potential difference × Current.</p> Signup and view all the answers

    In a parallel circuit, what is true about the potential difference across each component?

    <p>It is equal for each component.</p> Signup and view all the answers

    If two resistors are connected in parallel, how does the total resistance compare to the smallest resistor?

    <p>It is less than the smallest resistor.</p> Signup and view all the answers

    What is the effect of temperature on the resistance of a thermistor?

    <p>Resistance decreases as temperature increases.</p> Signup and view all the answers

    Which wire in a three-core cable is primarily responsible for safety?

    <p>Earth wire.</p> Signup and view all the answers

    What is the effect of combining resistors in parallel on the total current in the circuit?

    <p>Total current increases.</p> Signup and view all the answers

    Which of the following statements is true about the National Grid?

    <p>It includes both step-up and step-down transformers for efficient energy transfer.</p> Signup and view all the answers

    How is the total potential difference used in a series circuit?

    <p>It is accumulated across components.</p> Signup and view all the answers

    What characterizes the current through an ohmic conductor?

    <p>It is directly proportional to potential difference at constant temperature.</p> Signup and view all the answers

    What is the significance of the amount of current at different points of a closed loop circuit?

    <p>It is the same at all points.</p> Signup and view all the answers

    What determines the total equivalent resistance in a series circuit?

    <p>The total resistance is the sum of individual resistances.</p> Signup and view all the answers

    How does adding resistors in parallel affect total resistance?

    <p>It decreases the total resistance.</p> Signup and view all the answers

    What does the equation E = P t represent?

    <p>Energy transferred equals power times time.</p> Signup and view all the answers

    When analyzing a circuit, what does adding more components in parallel accomplish?

    <p>Allows for more current pathways, decreasing total resistance.</p> Signup and view all the answers

    What happens to the overall current when resistors are connected in parallel?

    <p>The overall current increases.</p> Signup and view all the answers

    What occurs to the resistance of a filament lamp as its temperature increases?

    <p>The resistance increases.</p> Signup and view all the answers

    How does the earth wire function in a three-core cable?

    <p>Provides a path for excess current in case of a fault.</p> Signup and view all the answers

    Which of the following statements best explains why the National Grid is efficient?

    <p>It relies on increasing potential differences for transmission to decrease current.</p> Signup and view all the answers

    What type of potential difference is supplied by domestic mains electricity in the UK?

    <p>Alternating current at 230 V.</p> Signup and view all the answers

    What is the relationship between power, current, and resistance in a circuit as expressed by P = I²R?

    <p>Power increases with the square of current.</p> Signup and view all the answers

    Which component's resistance varies with temperature?

    <p>Filament lamp.</p> Signup and view all the answers

    What equation represents the energy transferred in terms of charge flow and potential difference?

    <p>E = Q × V.</p> Signup and view all the answers

    What is the result of connecting multiple resistors in series?

    <p>The total resistance equals the sum of individual resistances.</p> Signup and view all the answers

    What is the relationship between current and charge flow in a circuit?

    <p>Charge flow is the product of current and time.</p> Signup and view all the answers

    In a series circuit, how does the total potential difference behave?

    <p>It is the sum of the potential differences across all components.</p> Signup and view all the answers

    What happens to the total resistance when resistors are connected in parallel?

    <p>It decreases and is less than the smallest individual resistor.</p> Signup and view all the answers

    If two resistors with resistance values of 4 Ω and 6 Ω are connected in series, what is their total resistance?

    <p>10 Ω</p> Signup and view all the answers

    What characterizes the current at any point in a closed loop circuit?

    <p>It is constant throughout the circuit.</p> Signup and view all the answers

    Why does adding resistors in series increase the total resistance?

    <p>Each additional resistor adds its resistance to the circuit.</p> Signup and view all the answers

    What is the total current in a parallel circuit when resistors of 2 A and 3 A are connected?

    <p>6 A since it's the sum of individual currents.</p> Signup and view all the answers

    How should one qualitatively explain the effect of adding resistors in parallel on the total current?

    <p>It allows more paths for current to flow, increasing total current.</p> Signup and view all the answers

    What property is true for components in a parallel circuit regarding voltage?

    <p>The voltage across each component is the same.</p> Signup and view all the answers

    What is the effect of combining two resistors of 5 Ω and 10 Ω in series on total resistance?

    <p>Resistance increases to 15 Ω.</p> Signup and view all the answers

    Study Notes

    Electrical Circuits

    • Electrical charge flows through a closed circuit if it includes a potential difference source.
    • Electric current is the flow of electrical charge, measured in amperes (A).
    • Charge flow (Q, in coulombs, C) = current (I) × time (t, in seconds, s).
    • Current is constant at any point in a closed loop.

    Series Circuits

    • Components connected in series have the same current.
    • The total potential difference of the power supply is split among the components.
    • Total resistance of two series components = sum of individual resistances (Rtotal = R1 + R2).
    • Resistances are measured in ohms (Ω).

    Parallel Circuits

    • Components connected in parallel have the same potential difference across each.
    • Total current through the circuit = sum of currents through individual components.
    • Total resistance of two parallel resistors is less than the smallest individual resistor.

    Resistor Types and Characteristics

    • Some resistors have constant resistance (ohmic conductors), others change with current.
    • Ohmic conductors (constant temperature): current is directly proportional to potential difference, and resistance remains constant.
    • Filament lamps: resistance increases with filament temperature.
    • Diodes: only allow current in one direction, very high resistance in the reverse direction.
    • Thermistors: resistance decreases with temperature increase.
    • Light-dependent resistors (LDRs): resistance decreases with increasing light intensity.

    Mains Electricity

    • Mains electricity uses a three-core cable:
      • Live wire (brown): carries alternating potential difference (mains supply).
      • Neutral wire (blue): completes the circuit.
      • Earth wire (green and yellow stripes): safety wire to prevent appliance becoming live (0V).
    • Potential difference between live and earth wires is approximately 230V.
    • Neutral wire is close to earth potential.
    • Earth wire carries current only in case of a fault.
    • Live wire can be dangerous even with a switch open.
    • Connecting the live wire to earth is extremely dangerous.
    • UK domestic supply is 50Hz alternating current (AC) and about 230V.
    • AC differs from Direct Current (DC).

    Power, Energy, and Appliances

    • Power (P, in watts, W) = potential difference (V) × current (I)
    • Power (P) = current (I)² × resistance (R)
    • Energy transferred (E, in joules, J) = power (P) × time (t)
    • Energy transferred (E)= charge flow (Q) × potential difference (V)
    • Different domestic appliances transfer energy (from batteries or AC mains) to kinetic energy of electric motors or heating devices.

    National Grid

    • The National Grid uses step-up transformers to increase potential difference to transmission cables and step-down transformers for domestic use.
    • This is an efficient way of transferring energy.

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    Description

    Test your knowledge on electrical circuits, including series and parallel connections, current flow, and resistance calculations. This quiz covers basic concepts critical for understanding how electrical systems function.

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