Advanced Science Primary 5 Systems

Study the diagram. Which switches must be closed for only Bulbs B1 and B2 to light up?

A S1, S2 and S3
B S1 and S3 only
C S1 and S2 only
D S2 and S3 only
Show Worked Solution

Worked Solution

Step 1: Identify the path for each bulb. S1 is the main switch. Step 2: B1 and B2 are in parallel with B3. S2 controls the branch with B1 and B2. Step 3: Closing S1 and S2 completes the path for B1/B2 but leaves the B3 path open.

Correct answer: S1 and S2 only

Want more questions like this? Superholic Lab has 10,000+ MOE-aligned questions with full worked solutions.

Start Free Trial — 7 Days Free