Voltage, Current, Power and Resistance
Use the relationships between voltage, current, power and resistance to interpret stated equipment and test data.
Prepare from maintenance duty to traceable decision
Start with responsibility and risk, classify the equipment, inspect before testing, choose relevant measurements, interpret all evidence and complete an honest record.
Core concepts
Concept 1
Use the relationships between voltage, current, power and resistance to interpret stated equipment and test data.
Exam cue: Choose the relationship from the known quantities, convert prefixes, calculate, then sense-check magnitude and unit against the equipment.
Concept 2
Ohm's law links voltage, current and resistance; electrical power can be related to voltage and current when the stated assumptions allow it.
Exam cue: Separate the evidence needed for the written decision from the live competence required to obtain it safely.
Concept 3
A calculated conductor resistance must be interpreted with lead resistance, length, cross-sectional area, connections and expected construction in view.
Concept 4
Written calculations use supplied data and assumptions; they do not replace an instrument reading or manufacturer limit.
Targeted study blocks
Purpose
Identify the safety decision
Use the relationships between voltage, current, power and resistance to interpret stated equipment and test data.
Method
Use an evidence-led sequence
Choose the relationship from the known quantities, convert prefixes, calculate, then sense-check magnitude and unit against the equipment.
Boundary
Preserve practical and legal limits
Written calculations use supplied data and assumptions; they do not replace an instrument reading or manufacturer limit. Do not use a formula before converting milliamperes, kilohms or megohms to a consistent scale.
Risk pitfalls and guardrails
Do not use a formula before converting milliamperes, kilohms or megohms to a consistent scale.
Guardrail: Inspect first, use only relevant tests and keep the written decision within the practical and legal boundary.
Do not treat a fixed interval, one reading or a test label as the complete maintenance decision.
Guardrail: Inspect first, use only relevant tests and keep the written decision within the practical and legal boundary.
Memory anchors
Voltage, Current, Power and Resistance: purpose
Use the relationships between voltage, current, power and resistance to interpret stated equipment and test data.
Voltage, Current, Power and Resistance: method
Choose the relationship from the known quantities, convert prefixes, calculate, then sense-check magnitude and unit against the equipment.
Voltage, Current, Power and Resistance: key fact 1
Ohm's law links voltage, current and resistance; electrical power can be related to voltage and current when the stated assumptions allow it.
Voltage, Current, Power and Resistance: key fact 2
A calculated conductor resistance must be interpreted with lead resistance, length, cross-sectional area, connections and expected construction in view.
Voltage, Current, Power and Resistance: boundary
Written calculations use supplied data and assumptions; they do not replace an instrument reading or manufacturer limit.
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
A 230 V heater draws 4 A. Ignoring power factor, what power does it take?
A 1,150 W appliance operates at 230 V. What current does it draw, assuming a resistive load?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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