Current, Voltage, Resistance and Circuit Basics
Use the relationship between voltage, current and resistance to explain circuit behaviour and why a hazardous voltage can drive harmful current.
How to prepare for the ECS Electrical Safety Unit
Learn the official knowledge map, practise source-led stop-and-handover decisions and reinforce practical procedures only through suitable training and authorised supervision.
Core concepts
Concept 1
voltage as potential difference
Exam cue: Write V = I × R before rearranging and keep units visible.
Concept 2
current as charge flow
Exam cue: A protective device does not make contact with live parts safe.
Concept 3
resistance and continuity
Concept 4
Ohm's law
Concept 5
series and parallel paths
Targeted study blocks
Knowledge
What this topic establishes
Use the relationship between voltage, current and resistance to explain circuit behaviour and why a hazardous voltage can drive harmful current.
Boundary
Where written knowledge stops
Simple calculations support hazard recognition; they do not justify live measurement, design work or alteration outside competence.
Application
How to reason through a scenario
Identify the requested quantity, select the correct form of Ohm's law, convert units, calculate and check whether the result is physically plausible.
Risk pitfalls and guardrails
confusing current with voltage
Guardrail: Do not convert basic assessment knowledge into permission to perform a safety-critical practical task.
dropping unit conversions
Guardrail: Do not convert basic assessment knowledge into permission to perform a safety-critical practical task.
treating body resistance as fixed
Guardrail: Do not convert basic assessment knowledge into permission to perform a safety-critical practical task.
Memory anchors
Ohm's law?
V = I × R; therefore I = V ÷ R and R = V ÷ I.
Unit of current?
The ampere (A).
Unit of resistance?
The ohm (Ω).
Why does wet or damaged skin increase danger?
Lower resistance can allow more current to flow for the same contact voltage.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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