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 current in an inductor cannot change instantly, using ℰ = −L dI/dt. (Guide: “What an inductor does in a circuit”; Practice Q2)
- I can explain why an inductor acts as a wire with zero resistance after a long time. (Guide: “What an inductor does in a circuit”; Practice Q5(a))
- I can give the three meanings of τ: the initial-rate time, 63% of the final current when growing, and 37% of the starting current when decaying. (Guide: Figure 1; Practice Q3, Q5)
- I can explain where the inductor’s stored energy goes when the current dies away. (Guide: “Energy in an LR circuit”; Practice Q6(d))
Calculation and skills
- I can apply the loop rule to a series LR circuit to get ℰ = IR + L dI/dt and solve it by separating variables. (Guide: “The loop rule and the differential equation”; Practice Q7)
- I can calculate τ, the final current, I(t), V_L(t) and the time to reach a given current. (Guide: Worked example 1; Practice Q1, Q4)
- I can find the currents in every branch just after and long after a switch moves. (Guide: Worked example 2; Practice Q6)
- I can check energy conservation using ℰI = I²R + LI dI/dt. (Practice Q4)
- I can find τ and L from experimental current–time data, including with a straight-line graph. (Practice Q5)
- I can sketch current and voltage against time with the correct starting values and asymptotes. (Guide: Figure 1; Practice Q6(e))
Reasoning
- I can choose the right resistance for τ when growth and decay happen through different loops. (Guide: Worked example 2; Practice Q6)
- I can explain why opening a switch can give a potential difference larger than the battery emf. (Guide: Worked example 2; Practice Q6(c))
- I can derive the equation for a circuit with two resistors and one inductor and check it in a limiting case. (Practice Q7)
- I can predict how changing L or R changes τ and the final current. (Practice Q5(e))
All ticked? Move on to Topic 13.6, LC circuits, or return to the course roadmap.