Previous Knowledge : Students must be aware of the concepts like voltage, current and resistance. They must have done practicals with simple electrical circuits.
Objective :
In a series circuit, current remains the same across each resistance, because there is only a single path for the flow of the entire charge. Hence, if one of the components in the electrical circuits don't work properly then the electrical circuits will not work as the current flow is disrupted. Whereas, in the case of a parallel circuit the voltage remains the same and there is branching of current. Hence even if a component fails it won’t affect the functioning of other components as there is alternative path for current to flow. In the series circuit the total resistance is greater than highest resistance in the circuit and in the parallel circuit it is less than the lowest resistance in the circuit. In series circuit, the current across each component is the same whereas in the parallel the total current is the sum of the current across each branch.
Activity for introducing Series/ Parallel Electrical Circuits:
Materials:
Voltage source
Bulbs of equal wattage
Bulb holders
Procedure:
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Divide students into groups and provide them with above materials. Direct them to write down their observation, that is, the brightness of the bulbs in each case. Let them make series and parallel electrical circuits as shown in the figures. ( the figure above is the series circuit and the figure below is the parallel circuit) Instruct them to use bulbs instead of the resistors in the figures. Now instruct them to remove one bulb from each electrical circuits and record the change. Let them increase the number of bulbs in both electrical circuits.
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In the actual electrical circuits the resistors are used instead of the bulbs. Usually, children find the transition from the bulbs to resistors a bit confusing. So solder series electrical circuits by connecting two resistors in series across a source as shown in fig 1 and another in parallel as shown in fig 2 ( use R1 = R2 ) and bring it to the classroom. Introduce them the multi-meter and the circuits. Instruct the students to closely observe the activity. First measure the voltage of the source and then the voltage and current across each resistors in series electrical circuits. Repeat the process with the parallel electrical circuits also. Break the circuit by removing one resistor from each electrical circuits and measure the current across the remaining resistor in each electrical circuits.
Analysis and conclusion:
From the analysis of the recorded observations children will understand that, when two or more bulbs are connected in series across a voltage source they become dimmer as the number of bulbs increase whereas, if the same is connected in parallel all the bulbs shine with equal brightness. Bulbs shine more brightly in parallel electrical circuits than in series. They will arrive at a conclusion that in series the bulbs become dimmer as voltage gets divided across each component and it is of equal brightness as it is the same across each component in parallel electrical circuits. Also, they will understand that the electrical circuits are broken in series when one bulb is removed but the flow is uninterrupted in parallel electrical circuits.
Conclusion:
Usually, middle class students find it difficult to solve the actual electrical circuits as teachers mainly use bulbs to teach series and parallel electrical circuits. In order to solve this problem this lesson plan has used actual electrical circuits. As a home work activity instruct students to find the type of electrical circuits we use in our houses.
