O level Use the following learning outcomes to design a lesson to learn O level science physics Learning Outcomes (a) draw circuit diagrams with power sources (cell or battery), switches, lamps, light-emitting diodes (LEDs), resistors (fixed and variable), fuses, ammeters and voltmeters (b) state that the current at every point in a series circuit is the same and apply the principle to new situations or to solve related problems (c) state that the sum of the potential differences in a series circuit is equal to the potential difference across the whole circuit and apply the principle to new situations or to solve related problems (d) state that the sum of the currents in the separate branches of a parallel circuit is equal to the current from the source and apply the principle to new situations or to solve related problems (e) state that the potential difference across the separate branches of a parallel circuit is the same and apply the principle to new situations or to solve related problems (f) recall and apply the formulae for the effective resistance of a number of resistors in series and in parallel to new situations or to solve related problems (g) recall and apply the relevant relationships, including R = V / I and those for current, potential differences and resistors in series and in parallel circuits, in calculations involving a whole circuit.

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Circuit diagrams use standard symbols to represent electrical components. A cell provides electrical energy with one positive and one negative terminal. A battery contains multiple cells. Switches control current flow. Lamps and LEDs convert electrical energy to light. Resistors limit current flow, with variable resistors allowing adjustment. Ammeters measure current and must be connected in series. Voltmeters measure potential difference and connect in parallel. Fuses protect circuits by breaking when current is too high. A series circuit connects components end-to-end in a single path. The key principle is that current flows the same everywhere in the circuit - what goes in must come out. This is because there's only one path for electrons to follow. However, voltage behaves differently. Each component uses up some voltage, and the sum of all individual voltages equals the total battery voltage. This is like water flowing through pipes of different sizes - the flow rate stays constant, but pressure drops across each restriction. Parallel circuits provide multiple paths for current to flow. Unlike series circuits, each branch connects directly to the power source, so voltage across each branch is the same as the battery voltage. However, current behaves differently - it splits at junctions. The total current from the battery equals the sum of currents through each branch. This is like water flowing through multiple pipes - each pipe gets the same pressure, but the total flow divides between them based on resistance. Ohm's law states that resistance equals voltage divided by current. For resistors in series, we simply add their values together. For parallel resistors, we use the reciprocal formula - one over the total resistance equals the sum of one over each individual resistance. In our example with 2 ohm and 3 ohm resistors, series gives us 5 ohms total, while parallel gives us 1.2 ohms. The triangle diagram helps remember Ohm's law relationships - cover the unknown quantity to see the formula. Complex circuits combine series and parallel sections. To analyze them systematically: first identify which components are in series or parallel. Calculate equivalent resistance for parallel sections, then add series resistances. Use Ohm's law to find total current from the battery. Finally, calculate individual branch currents and voltages. In this example, the 2-ohm and 3-ohm resistors are in parallel, giving 1.2 ohms equivalent resistance. Adding the series 2-ohm resistor gives 3.2 ohms total, so current is 12 volts divided by 3.2 ohms equals 3.75 amperes.