Advanced Science Primary 5 Systems

Study the circuit below. Which switch(es) must be closed for Bulb B1 to light up but NOT Bulb B2?

A S2 and S3
B S1 and S2
C Only S1
D S1 and S3
Show Worked Solution

Worked Solution

Step 1: Identify S1 as the main switch and S2/S3 as branch switches. Step [2-9]: S1 must be closed for any current to flow from the battery. Step [2-9]: S2 controls B1's branch, so closing S1 and S2 completes B1's path while B2 remains unlit.

Correct answer: S1 and S2

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