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
- What is electric current and what conditions are required for it to flow?
- Explain the relationship between potential difference (voltage) and the flow of current.
- Define resistance and describe its role in an electrical circuit.
- What is the formula for calculating charge, and what are the units of measurement for each variable?
- Describe the function of a battery in an electrical circuit.
- Explain the difference between an open and a closed switch in a circuit.
- What is the purpose of a fuse in an electrical circuit?
- What is the symbol and function of an ammeter?
- Differentiate between the symbols for a filament lamp and an LED.
- How is a variable resistor represented in a circuit diagram, and what does it do?
Answer Key
- Electric current is the flow of electrical charge. It only flows in a complete (closed) circuit if there is a source of potential difference.
- 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.
- 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.
- 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).
- A battery acts as a source of potential difference in a circuit, providing the energy to “push” the electric charge through the circuit.
- An open switch breaks the circuit, preventing the flow of current. A closed switch completes the circuit, allowing current to flow.
- 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.
- 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.
- 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.
- 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
- Explain the relationship between voltage, current, and resistance in a circuit.
- Describe the difference between an Ohmic and a non-Ohmic conductor.
- How does the resistance of an LDR change with light intensity?
- Explain why the total resistance in a series circuit increases when another resistor is added.
- State two key differences between series and parallel circuits.
- How does the total current in a parallel circuit relate to the currents in the individual branches?
- Why does adding a resistor in parallel decrease the total resistance of a circuit?
- Explain how a thermistor can be used in a temperature sensing circuit.
- 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?
- Two identical bulbs are connected in parallel to a 12V battery. What is the voltage across each bulb?
Answer Key
- 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.
- 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.
- The resistance of an LDR decreases as light intensity increases. In darkness, it has high resistance, and in bright light, its resistance is low.
- 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.
- 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.
- The total current entering a junction in a parallel circuit is equal to the sum of the currents flowing out through each branch.
- 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.
- 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.
- Total resistance (R) = 2Ω + 3Ω = 5Ω. Using Ohm’s Law (V = IR), total voltage (V) = 1A × 5Ω = 5V.
- In a parallel circuit, the voltage across each branch is equal to the source voltage. Therefore, the voltage across each bulb is 12V.