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
Two straight bus-bars in a laboratory supply carry equal currents in the same direction. The separation is and the measured force per metre is .
Total: 5 marks
(a) State whether the bus-bars attract or repel. (1 mark)
(b) Find the current in each bus-bar. (3 marks)
(c) What happens to the force per metre if the separation is doubled? (1 mark)
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