Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can explain why the external field exerts a force on the current it induces in a conductor. (Guide: “The field pushes on the current it induces”)
- I can identify which segments of a loop feel a magnetic force and which forces cancel. (Guide: Figure 1; Practice Q1, Q5)
- I can use Lenz’s law to show that the force opposes the motion, both entering and leaving a field. (Practice Q1, Q3)
- I can explain why a loop moving wholly inside a uniform field feels no magnetic force. (Practice Q3, Q7)
- I can describe how forces on an induced current produce a torque that opposes rotation. (Guide: “Turning effects”)
Calculation and skills
- I can calculate the induced current and the force F = B²L²v/R on a moving rod or loop edge. (Guide: Worked example 1; Practice Q4, Q5)
- I can write Newton’s second law for a moving conductor and solve it for v(t). (Guide: Worked example 2; Practice Q6)
- I can find a terminal speed by setting the acceleration to zero. (Practice Q6, Q7)
- I can sketch v against t and mark the time constant τ = mR/(B²L²). (Guide: Figure 2; Practice Q6)
Reasoning
- I can predict factors of change in current, force and power when v, B, L or R changes. (Guide: factor-of-change table; Practice Q2, Q4)
- I can show that the mechanical power supplied equals the power dissipated, I²R. (Practice Q4, Q6, Q7)
- I can explain why constant-acceleration equations do not apply to magnetic braking. (Practice Q5)
All ticked? Move on to Topic 13.4, Inductance.