Explain the advantages of parallel lamp connections
Connect lamp independence and full branch p.d. to the wiring while keeping common-source failures separate.
Cross-referenced from the related Cambridge IGCSE Chemistry 0620 or Physics 0625 teaching to the 0652 syllabus. Exact 0652 Core/Supplement objective coverage and this final-series course’s examiner fit still need specialist review. Written practice is self-checked and does not predict a Cambridge grade or demonstrate supervised laboratory competence.
Before you begin
- Recognize parallel endpoint pairs.
- Interpret common and branch switches.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What happens when one lamp opens in a sole series path?
What you will learn
- Explain parallel lighting advantages.
- Distinguish one branch failure from a shared interruption.
Give each lamp its own branch
Lamps in parallel each have a complete path across the same source endpoints, so each receives the source p.d. in the ideal wiring model. They can be designed to operate at their intended supply p.d. rather than share the source p.d. as series lamps do. Appropriate lamp ratings remain necessary.
A switch in one lamp branch can control that lamp independently. If one filament fails open, its branch is interrupted while another complete branch can stay powered. A single broken series lamp interrupts the sole series path and stops all those lamps.
Describe the limitations correctly
A common source switch, a failed source or a break in a shared feed can still stop all parallel lamps. Independence concerns separate branches with the source and shared connections intact; it is not immunity from every fault. A short-circuit branch is also different from a failed-open filament.
Brightness comparisons require lamp characteristics and source behaviour. Identical appropriately rated lamps across an ideal fixed-p.d. source have matched operating conditions, but unlike lamps need not have equal brightness. These schematic advantages are curriculum reasoning, not instructions to construct mains lighting.
Sources for this lesson
Pause and explain
A common source switch opens for two parallel lamps. What follows?
Worked example
Two parallel lamps have separate branch switches. One filament fails open. What can happen to the other lamp?
Show the worked solution
- Only the failed branch is interrupted.
- The other lamp keeps a complete path across the source.
- It can remain powered if shared connections and the source stay intact.
Answer The other lamp can stay on under intact shared-source conditions.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Draw two parallel lamps with separate branch switches and explain independent control.
Give me a hint
Keep each switch inside its own A-to-B lamp path.
Compare my reasoning
- Draw two lamp branches across common source junctions.
- Place a switch in each branch.
- Opening one switch interrupts only that branch when the shared source remains intact.
Two independently switched branches; either lamp can be controlled separately.
Look for these in your work
- Locate each switch in its branch.
- Keep the source return common.
Compare one failed-open filament in a two-lamp series circuit and a two-lamp parallel circuit.
Give me a hint
Trace the surviving complete paths in each arrangement.
Compare my reasoning
- Series has one path, interrupted by either open filament.
- Parallel has another independent lamp path.
- With the source intact, the other parallel lamp can remain powered.
Series: both off; parallel: the other can remain on with shared source intact.
Look for these in your work
- State the failed-open condition.
- Check shared-source continuity.
A learner promises identical brightness for any two parallel lamps and says no fault can stop both. Correct both claims.
Give me a hint
Separate branch p.d., device behaviour and shared components.
Compare my reasoning
- Parallel lamps share endpoint p.d.
- Unlike lamp characteristics need not give equal brightness.
- A shared source or feed interruption can stop both.
Same branch p.d. does not guarantee unlike-lamp brightness; shared interruptions can stop all lamps.
Look for these in your work
- Correct both promises.
- Keep the valid parallel advantages.
Common mistakes
- A failed-open branch is different from a short.
- Parallel does not prevent shared-source interruption.
- Brightness needs lamp and source conditions.
What can you explain now?
Why can one lamp be switched independently in parallel?
Compare with the explanation
Its switch can interrupt only its own branch.
The other branch still connects across the source if shared connections remain intact.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain full branch p.d., independent switches and failed-open lamp behaviour with shared-source limits.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.