Explain the advantages of high-voltage transmission
Compare current and cable heating qualitatively for the same transferred power with cable conditions matched.
Section 4.5.6 · The transformer
Core and Extended; Physics 0625, 2026–2028. Use the stated source, operating conditions and meter ranges. Written practice is self-checked.
Before you begin
- Use power as a transfer rate.
- Understand resistance and heating.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which comparison isolates the stated voltage advantage?
What you will learn
- Compare current and cable heating qualitatively for the same transferred power with cable conditions matched.
- Explain lower current and heating for matched power while retaining cable, insulation and downstream supply limits.
Compare the same power transfer
For the same specified electrical power transfer, a greater transmission voltage permits a smaller current. A smaller current reduces heating loss in the same resistive cable. This is the main benefit of high-voltage transmission, not a claim that high voltage is always safer or that cable resistance becomes zero.
Match the transferred power and cable resistance when making the comparison. Comparing a high-voltage system transferring much more power with a low-power low-voltage system does not isolate the voltage effect. The quantitative square-current loss explanation is developed in Supplement work.
State practical advantages without removing trade-offs
Reduced loss allows more of the source energy to reach the intended load under suitable stated conditions. For a chosen loss allowance, transmission design can also use less conducting material than a comparable higher-current arrangement, but conductor and mechanical requirements still matter.
High voltage requires suitable insulation, clearances and equipment. Transformers later reduce voltage for specified use. A conceptual advantage is not permission to handle high-voltage equipment; actual network design needs specialist specifications and approval.
Pause and explain
Does higher transmission voltage make cable resistance zero?
Worked example
Two supplied transmission arrangements transfer the same power through cables with the same resistance. One has greater voltage. Compare current and heating loss qualitatively.
Show the worked solution
- Keep transferred power and cable conditions matched.
- Higher voltage permits lower current.
- Lower current reduces resistive heating loss.
Answer Lower current and lower cable heating loss at the greater voltage.
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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.
Explain the heating advantage at matched power and cable resistance.
Give me a hint
Connect voltage, current and heating in order.
Compare my reasoning
- Greater voltage permits smaller current for the same power.
- The cable still has resistance.
- Smaller current gives less resistive heating loss.
Lower current reduces cable heating loss.
Look for these in your work
- State the matched-power condition.
- Retain finite resistance.
Why can a changed cable material confound a voltage-loss comparison?
Give me a hint
Heating depends on the cable as well as the current.
Compare my reasoning
- Different material can change resistance.
- Heating can change for that separate reason.
- Match cable resistance to isolate the voltage comparison.
Changed resistance is an additional heating-loss factor.
Look for these in your work
- Identify resistance.
- Propose the required control.
A report says high-voltage transmission is loss-free and needs no later voltage reduction. Correct it.
Give me a hint
Separate reduced loss from zero loss and user-supply conditions.
Compare my reasoning
- Finite cable resistance can still cause heating.
- Transformers and other stages can also have losses.
- Later equipment requires its specified voltage stage.
Losses are reduced, not universally zero; suitable step-down stages remain necessary.
Look for these in your work
- Correct the loss claim.
- Retain the supplied-use requirement.
Common mistakes
- Match power and cable resistance.
- Resistance does not vanish.
- Retain insulation and design limits.
What can you explain now?
What is the central high-voltage transmission advantage?
Compare with the explanation
Lower current and less cable heating for matched power
The matched power can be transferred with lower current and smaller resistive heating losses.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain lower current and heating for matched power while retaining cable, insulation and downstream supply 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.