Simple Circuits
Year 7 ⚡ Electricity & Magnetism Build and describe series circuits; understand current, voltage and components.
🔌 Circuit Components
A basic circuit needs: a power source (battery/cell), conductors (wires), and components (bulbs, resistors, switches).
| Component | Symbol | Function |
|---|---|---|
| Cell/Battery | ⊣⊢ | Provides EMF (voltage) |
| Resistor | Rectangle | Opposes current flow |
| Bulb/Lamp | Circle with X | Converts electrical to light |
| Switch | Gap in wire | Opens/closes circuit |
| Ammeter | Circle A | Measures current (in series) |
| Voltmeter | Circle V | Measures voltage (in parallel) |
⚡ Current & Voltage
Current (I) is the flow of charge; measured in Amperes (A). Voltage (V) is the energy per unit charge; measured in Volts (V).
Key Relationship
$$Q = It \qquad \text{(charge = current × time)}$$ Current flows from + to − (conventional current). Electrons actually flow from − to +.
🔗 Series Circuits
In a series circuit: same current everywhere, voltages add up, total resistance = sum of all resistances.
Series Rules
$$I_{\text{same}} \qquad V_T = V_1 + V_2 \qquad R_T = R_1 + R_2$$
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🔌 Circuit Simulator