The document you provided contains several electrical circuit problems related to impedance, current, voltage, phase difference, Thevenin equivalent circuits, and superposition principles. Here is an outline of the solution approach for each of the questions:

Problem 1: Circuit Analysis for Figure 1

1. Total Impedance (Z):

   • If the circuit consists of resistors, capacitors, and inductors, the total impedance can be found by combining the individual impedances:
     • For resistors: $Z_R = R$
     • For inductors: $Z_L = j\omega L$
     • For capacitors: $Z_C = \frac{1}{j\omega C}$
   • Use series and parallel combinations depending on the configuration.

2. Current $i(t)$:

   • Apply Ohm's law to find the current: $i(t) = \frac{V_{source}}{Z_{total}}$
   • Here, $V_{source}$ is the input voltage, and $Z_{total}$ is the total impedance.

3. Voltage across the 0.1H inductor:

   • Use the formula for voltage across an inductor: $v_L(t) = L \frac{di(t)}{dt}$ where $L = 0.1H$ and $\frac{di(t)}{dt}$ is the time derivative of the current.

4. Phase Difference:

   • The phase difference between voltage and current in inductive or capacitive circuits can be calculated based on impedance. For inductors, current lags voltage by 90 degrees.

Problem 2: Thevenin Equivalent for Figure 2

• To find the Thevenin equivalent:
  1. Remove the load from terminals a-b.
  2. Find the open-circuit voltage (Thevenin voltage).
  3. Find the Thevenin impedance by deactivating all independent sources (voltage sources shorted, current sources open).

Problem 3: Superposition Principle

• Superposition involves solving for $I_1$, $I_2$, and $I_3$ by considering one independent source at a time, turning off the others (replacing voltage sources with shorts and current sources with open circuits), and then combining the effects.

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Here are 5 follow-up questions to expand on the material:

1. How does impedance vary with frequency in an RL circuit?
2. What is the physical interpretation of phase difference in AC circuits?
3. Can Thevenin's theorem be applied to non-linear circuits? Why or why not?
4. How does the superposition principle simplify the analysis of complex circuits?
5. What are the conditions under which inductive reactance dominates over resistance?

Tip: For AC circuit analysis, always pay attention to the frequency, as it affects the reactance of inductors and capacitors significantly.