Charge flow in circuits | Year 7 Physics (Cambridge) PDF Download

Understanding Electrical Circuits

An electrical circuit is a closed loop that includes a power source, such as a cell or battery, and components through which electrons flow. It can be represented using circuit diagrams.

Components of a Circuit

• Cell/Battery Symbol: Represents the power source. A battery is made up of two or more cells connected together.
• Filament Lamp Symbol: Represents a light bulb. When connected in a circuit with a closed switch, it lights up.
• Switch Symbol: Controls the flow of current. When closed, it allows current to flow; when open, it interrupts the circuit.

Key Terms

• Current (I): Measures the flow of electrons in the circuit, similar to water flow in a pipe. It is measured in amperes (A).
• Potential Difference (V): Also known as voltage, it is the driving force that pushes electrons through the circuit, provided by the cell or battery. It is measured in volts (V).
• Resistance (R): Opposes the flow of electrons, similar to partial blockage in a pipe. It is measured in ohms (Ω).

Direction of Current

• Current flows from the positive terminal (longer line) of the cell/battery to the negative terminal (shorter line), though historically, conventional current is considered to flow from positive to negative.

Circuit Representation

• Simple Circuit: Contains a single power source, such as a cell, connected in a closed loop with components like lamps and switches.
• Complex Circuits: Use various components like resistors, capacitors, and diodes, represented by specific symbols in circuit diagrams.

Conclusion

Understanding electrical circuits involves grasping the roles of current, potential difference, and resistance. These concepts are crucial in explaining how electricity flows through different components in both simple and complex circuits.