Case study·Hard exam skill (4/5)·Calculator allowed
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
A small power station has to transmit of power. It can transmit at directly or use a step-up transformer to transmit at before stepping down near homes.
Total: 5 marks
(a) Find the line current if transmission is at 250 V. (1 mark)
(b) Find the line current if transmission is at 5000 V. (1 mark)
(c) Find the ratio of resistive line losses in the two cases, assuming the same line resistance. (2 marks)
(d) State why transformers are used in power transmission. (1 mark)
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