Science Topic Test: Electricity Year 8

Key Words

  • Current: The flow of electric charge.

  • Independent variable: The variable you change in an investigation to see how it affects the dependent variable.

  • Dependent variable: The variable you measure or observe.

  • Control variable: A variable that could affect the dependent variable so must be kept the same.

Circuit Diagrams

Electrical circuits are often represented by circuit diagrams. They are simple and easy to interpret. Circuit symbols are used to represent the components used in a circuit.

  • Switch (open): --o/o--

  • Switch (closed): --o--o--

  • Bulb: ---X---

  • Cell: ---|!---

  • Battery: ---|!|!---

  • Ammeter: ---A---

  • Voltmeter: ---V---

  • Motor: ---M---

Series Circuits

In a series circuit, elements are connected end-to-end in a single loop. If one bulb breaks, none of the bulbs will light up because the circuit is no longer complete. The current is the same everywhere in a series circuit. It doesn't matter where you place the ammeter; it will always show the same reading. More cells or batteries in the circuit lead to greater current. Current is not used up.

Parallel Circuits

In a parallel circuit, elements are connected on separate branches. This provides different paths for the current to flow. If one bulb stops working, the other bulbs will remain lit as the circuit is still complete. The current is split between the branches in a parallel circuit.

Current

Current is the flow of electrical charge around a circuit. The faster the flow of charge, the higher the current. Current is measured in amps (A) using an ammeter. An ammeter is connected in series with the component.

Batteries

Batteries store chemical energy and convert it into electrical current within a circuit. Batteries contain an electrolyte and two electrodes. One electrode is positively charged, and the other is negatively charged. A chemical reaction between the two electrodes generates a flow of electrical energy to the circuit.

Modelling Circuits

Scientists frequently use models to help explain complex concepts. Some models are more effective than others. For example, in the boiler and radiator model, the pump acts like a battery, pushing charges (like water) around the circuit (pipes). The radiator (like a component) transfers energy to its surroundings. This analogy helps visualize how energy and charge move through an electrical circuit.