FE Electrical & Computer Practice Question Solution included after investigation
CASE E-030 · FE

The Feeder That Delivered 228 V Instead of 240 V

The source measured 240 V. The load saw only 228 V because the feeder resistance was treated as one-way.

▶ INTERACTIVE CASE FILE • 5–10 MIN • CLICK TO INVESTIGATE

Inspect, commit, prove, fix, and sign off.

Case E-030 engineering failure visual
HOW THIS WORKS

Think like
a real engineer.

Follow the investigation process used in the field — in five guided steps.

1

Inspect

Review the problem, diagram, and evidence.

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

SAME PRINCIPLES. HIGHER STANDARDS.
PROBLEM STATEMENT

A 240 V single-phase source supplies a 30 A load through a two-wire feeder. Each conductor has 0.20 Ω resistance. The design note predicts only a 6 V drop, but the load measures about 228 V. Diagnose the path error, calculate actual voltage drop and feeder loss, and choose a correction that cuts the drop in half.

Power Systems Electrical & Computer Design Verification Root Cause Analysis Safe Correction
E-030
INVESTIGATION WORKSPACE WORK THROUGH THE CASE — YOUR CHOICES MATTER.
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DEBRIEF (LOCKED)

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Find the root cause, confirm the fix, and see how this connects to the exam.

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CASE CLOSED · ENGINEERING VERDICT

What actually failed — and what should change.

What failed

The load received 228 V.

What was assumed

Only one conductor resistance was included.

Corrected model

Use full loop resistance for voltage drop and I²R loss.

QUICK ANSWER

For a two-wire single-phase feeder, current travels through both conductors. If each is 0.20 Ω, the loop is 0.40 Ω. At 30 A, the drop is 12 V, so a 240 V source delivers about 228 V.

ENGINEERING TAKEAWAY

Use total loop resistance: Rloop = Rout + Rreturn, then ΔV = I Rloop and Ploss = I² Rloop.

CASE QUESTIONS

Questions this case should settle.

Do you include both conductors in single-phase voltage drop?

Yes. Use the resistance of the complete out-and-back path.

What is the feeder loss at 30 A and 0.40 Ω?

I²R = 360 W.

NEXT FE PRACTICE QUESTION

The 8 Ohm Load That Became 128 Ohms

Power Systems · 5–10 min

Continue Practice →
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.