MATERIALS • three 1,5 V cells • three bulbs (resistors) • switch • connecting wires • circuit board


METHOD Step 1 Read through the activity and write a hypothesis and prediction for this investigation.


Step 2 Name the independent and the dependent variables. Step 3 Explain why this is a fair test.


Step 4 Conduct the investigation and record your results and conclusions.


Step 5 Connect the circuit as shown in Figure 1. Step 6 Observe the brightness of the bulb when you close the switch. Step 7 Connect a second resistor or light bulb in series with the first light bulb as shown in Figure 2.


Step 8 Observe the brightness of the bulbs when you close the switch. Step 9 Connect a third light bulb in series in the circuit. Step 10 Observe the brightness of the bulbs when you close the switch. Step 11 Unscrew one resistor or bulb in the circuit and observe what happens.


(3) (2) (3)


Figure 1 A circuit with three cells, one bulb and a switch


Figure 2 A circuit with three cells and two bulbs in series with one switch


RESULTS 1 Record your observations in a table. Do this each time another resistor or light bulb is added to the circuit. Rate the brightness on a scale of 1 to 10.


Number of resistors Brightness of bulbs


(3)


Unit 1 Series circuits and parallel circuits 119


STRAND 3


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