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22-Elec-A1 Circuits: December 2014

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

  1. Question 1 DC bridge network — equivalent resistance, current and power
  2. Question 2 Mesh analysis with a current source in the shared branch
  3. Question 3 First-order RL transient — switch opening
  4. Question 4 Superposition with two different-frequency sources
  5. Question 5 AC Thévenin equivalent and maximum power transfer
  6. Question 6 Laplace-domain solution of a switched RL circuit

Start with Question 1 →

Paper: National Examinations — 07-Elec-A1 Circuits, December 2014. Closed-book, 3-hour paper; a Laplace-transform table and Y–Δ formulas are supplied in the appendix. Six questions of equal value; any five constitute a complete paper. Full worked solutions to all six questions are given below so the set can be used for study regardless of which five a candidate chose.

Reference texts: C. K. Alexander & M. N. O. Sadiku, Fundamentals of Electric Circuits (7th ed., McGraw-Hill) — series/parallel reduction and the Wheatstone bridge, mesh/supermesh and nodal analysis, first-order transients, AC steady-state, Thévenin’s theorem and maximum-power transfer, and Laplace-domain circuit analysis; W. H. Hayt, J. E. Kemmerly & S. M. Durbin, Engineering Circuit Analysis (9th ed.) — companion treatment of the s-domain and initial-condition source models.

each network below is redrawn element-by-element from the original drawing. The Wheatstone bridge of Q1 is shown in the equivalent rectangular form (electrically identical to the diamond on the paper). Every reference node, mesh direction and source polarity used is stated with its solution so a reader can reproduce every sign. Phasor answers are quoted in magnitude∡angle form with angles in degrees; the source of Q5 is rms.