1
Inspect
Review the problem, diagram, and evidence.
FE Electrical & Computer Practice Question Solution included after investigation
CASE E-018 · FE
The Parallel Load That Tripped the Supply
Each branch looked safe. The supply still tripped the instant the second load was connected.
Inspect, commit, prove, fix, and sign off.
HOW THIS WORKS
Think like
Think like
a real engineer.
Follow the investigation process used in the field — in five guided steps.
2
Commit
Choose your hypothesis.
3
Prove
Run calculations and test your idea.
4
Fix
Select and validate a safe correction.
5
Sign Off
See the full debrief and key takeaways.
Case Brief
PROBLEM STATEMENT
A 12 V supply with 3 A over-current protection powers a 6 Ω load normally at 2 A. A 3 Ω load is then added in parallel. The technician expects the original 2 A source current to split between the two branches, but the protection trips. Determine the branch currents, the current demanded from the source, and why the technician's current-division model fails.
E-018
INVESTIGATION WORKSPACE
WORK THROUGH THE CASE — YOUR CHOICES MATTER.
🔒
DEBRIEF (LOCKED)
Complete the investigation
Complete the investigation
to unlock the full debrief.
Find the root cause, confirm the fix, and see how this connects to the exam.
to reveal
to reveal
to reveal
What actually failed — and what should change.
The added branch reduced equivalent resistance to 2 Ω, so the 12 V network demanded 6 A from a source protected at 3 A.
Current division does not mean total source current stays fixed when a voltage source drives a parallel network.
Use the common branch voltage to calculate each branch current, then sum branch currents to obtain the source-current demand.
Adding a resistor in parallel can increase the total current demanded from a voltage source because the equivalent resistance decreases while the source voltage remains the same. Here, 6 Ω in parallel with 3 Ω equals 2 Ω, so the 12 V network demands 6 A.
For parallel loads driven by a voltage source, each branch current is determined by the common branch voltage and that branch's resistance. Total source current is the sum of branch currents, so adding a parallel branch can increase source current.
Questions this case should settle.
Does adding a resistor in parallel increase total current?
For a fixed-voltage source, adding a parallel resistance lowers equivalent resistance and therefore increases the total current demanded from the source.
What current flows through 6 Ω and 3 Ω parallel branches at 12 V?
The 6 Ω branch requires 2 A and the 3 Ω branch requires 4 A, so the total source-current demand is 6 A.
Why does current division not mean total current stays fixed?
Current division describes how an existing total current distributes among parallel paths. With a voltage source, adding another branch changes the network equivalent resistance, so the total source current can change.
WHAT YOU’LL LEARN
Real failures. Lasting skills.
Each case is designed to build the judgment, analysis, and confidence you need for engineering exams — and beyond.
- Apply core engineering concepts to real-world problems
- Practice structured troubleshooting and analysis
- Strengthen exam-ready thinking through realistic scenarios
COMMON QUESTIONS
Do I need prior knowledge to use these cases?
Basic subject familiarity helps, but every case is designed to teach through the investigation itself.
How long does a case take?
Most cases are designed for a focused 5–10 minute investigation.
Are the cases aligned with engineering exams?
Each case is mapped to a verified exam, subject, topic, and misconception before publication.
What happens after I complete a case?
The sealed debrief unlocks with the root cause, corrected reasoning, fix, and takeaway.