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GCSE Physics Electricity and Circuits Revision Guide

GCSE Electricity and Circuits Podcast

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GCSE Electricity Key Terms

TermDefinitionElectric Current: The flow of electric charge through a conductor.

Potential Difference: The difference in electrical potential energy between two points in a circuit. Often referred to as voltage, it drives the flow of electric current.

ResistanceThe opposition to the flow of electric current. It determines how much current will flow for a given potential difference.

Ohm’s LawThe relationship between current, potential difference, and resistance: V = I * R (Voltage = Current x Resistance)

Circuit : A complete path through which electric current can flow.

Battery: A source of potential difference that converts chemical energy into electrical energy.

Switch: A device used to open or close a circuit, controlling the flow of current.

Fuse: A safety device that melts and breaks the circuit if the current exceeds a certain limit, protecting the circuit from damage.

Ammeter: An instrument used to measure electric current.

Voltmeter:An instrument used to measure potential difference.

Filament Lamp: An electric lamp that produces light by heating a thin filament wire to incandescence.

LED (Light Emitting Diode)A semiconductor device that emits light when current passes through it. More energy efficient than filament lamps.

Variable Resistor A resistor whose resistance can be adjusted, allowing for control of current in a circuit.Circuit DiagramA simplified representation of an electrical circuit using standard symbols to represent components and connections.

GCSE Electricity and Circuits Revision Guide

Key Concepts

1. Resistance and Ohm’s Law:

  • Resistance (R): The opposition a material offers to the flow of electric current, measured in Ohms (Ω).
  • Ohm’s Law: The relationship between voltage (V), current (I), and resistance (R). It states that V=IR, meaning voltage is directly proportional to current and resistance.

2. I-V Characteristics:

  • I-V Characteristic Graph: A graph that shows the relationship between current and voltage for a particular component.
  • Ohmic Conductor: A component that obeys Ohm’s Law, with a linear I-V characteristic.
  • Non-Ohmic Conductor: A component that does not obey Ohm’s Law, with a non-linear I-V characteristic (e.g., filament lamp, diode).

3. Circuit Components:

  • Resistor: A component designed to have a specific resistance.
  • LDR (Light Dependent Resistor): A resistor whose resistance changes with light intensity; higher resistance in darkness, lower in bright light.
  • Thermistor: A resistor whose resistance changes with temperature; usually lower resistance at higher temperatures.

4. Series Circuits:

  • Components are connected in a single loop, one after another.
  • Current is the same throughout the circuit.
  • Total voltage is shared between components.
  • Total resistance is the sum of individual resistances.

5. Parallel Circuits:

  • Components are connected on separate branches.
  • Voltage is the same across each branch.
  • Total current is the sum of currents in each branch.
  • Total resistance is less than the smallest individual resistance.

Quiz

  1. What is electric current and what conditions are required for it to flow?
  2. Explain the relationship between potential difference (voltage) and the flow of current.
  3. Define resistance and describe its role in an electrical circuit.
  4. What is the formula for calculating charge, and what are the units of measurement for each variable?
  5. Describe the function of a battery in an electrical circuit.
  6. Explain the difference between an open and a closed switch in a circuit.
  7. What is the purpose of a fuse in an electrical circuit?
  8. What is the symbol and function of an ammeter?
  9. Differentiate between the symbols for a filament lamp and an LED.
  10. How is a variable resistor represented in a circuit diagram, and what does it do?

Answer Key

  1. Electric current is the flow of electrical charge. It only flows in a complete (closed) circuit if there is a source of potential difference.
  2. Potential difference, also known as voltage, provides the “push” for the current to flow. The greater the potential difference across a component, the greater the current that flows through it.
  3. Resistance is anything that slows the flow down. It opposes the flow of current. A component with higher resistance will allow less current to flow for a given potential difference.
  4. Charge (Q) is calculated by multiplying the current (I) by the time (t) for which the current flows: Q = I * t. Charge is measured in coulombs (C), current in amperes (A), and time in seconds (s).
  5. A battery acts as a source of potential difference in a circuit, providing the energy to “push” the electric charge through the circuit.
  6. An open switch breaks the circuit, preventing the flow of current. A closed switch completes the circuit, allowing current to flow.
  7. A fuse is a safety device that protects a circuit from excessive current. It melts and breaks the circuit if the current exceeds a certain limit.
  8. The symbol for an ammeter is a circle with the letter “A” inside. An ammeter is used to measure the current flowing through a particular point in a circuit.
  9. A filament lamp is represented by a circle with a cross inside, while an LED is represented by a triangle with a line across its point and arrows pointing away from the base. Both are types of light sources.
  10. A variable resistor is represented by a rectangle with an arrow diagonally across it. It allows for adjustment of the resistance in a circuit, thereby controlling the amount of current flowing through.

GCSE Electricity  Quiz Part – 2 

  1. Explain the relationship between voltage, current, and resistance in a circuit.
  2. Describe the difference between an Ohmic and a non-Ohmic conductor.
  3. How does the resistance of an LDR change with light intensity?
  4. Explain why the total resistance in a series circuit increases when another resistor is added.
  5. State two key differences between series and parallel circuits.
  6. How does the total current in a parallel circuit relate to the currents in the individual branches?
  7. Why does adding a resistor in parallel decrease the total resistance of a circuit?
  8. Explain how a thermistor can be used in a temperature sensing circuit.
  9. A series circuit has two resistors, one with 2Ω resistance and the other with 3Ω resistance. If the current is 1A, what is the total voltage across the circuit?
  10. Two identical bulbs are connected in parallel to a 12V battery. What is the voltage across each bulb?

Answer Key

  1. Voltage is the driving force that pushes current through a circuit. Resistance is the opposition to current flow. Ohm’s Law states that voltage (V) is equal to current (I) multiplied by resistance (R), or V=IR.
  2. An ohmic conductor obeys Ohm’s Law, meaning its resistance remains constant as current changes, resulting in a linear I-V graph. A non-ohmic conductor does not obey Ohm’s Law, its resistance changes with current, resulting in a non-linear I-V graph.
  3. The resistance of an LDR decreases as light intensity increases. In darkness, it has high resistance, and in bright light, its resistance is low.
  4. In a series circuit, the total resistance is the sum of individual resistances. Adding another resistor increases the total path length for the current, thereby increasing the total resistance.
  5. In a series circuit, the current is the same throughout, while in a parallel circuit, the current splits between branches. The total resistance in a series circuit increases with added components, while in a parallel circuit it decreases.
  6. The total current entering a junction in a parallel circuit is equal to the sum of the currents flowing out through each branch.
  7. Adding a resistor in parallel creates an additional pathway for current to flow. This increases the overall conductivity of the circuit, effectively reducing the total resistance.
  8. A thermistor’s resistance changes with temperature. By incorporating a thermistor into a circuit, changes in its resistance can be used to detect and measure temperature variations.
  9. Total resistance (R) = 2Ω + 3Ω = 5Ω. Using Ohm’s Law (V = IR), total voltage (V) = 1A × 5Ω = 5V.
  10. In a parallel circuit, the voltage across each branch is equal to the source voltage. Therefore, the voltage across each bulb is 12V.

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