ISCET DC Circuits Fundamentals 3 — Questions and Answers
Question 1: Thevenin's theorem replaces a complex network with which equivalent circuit?
- A voltage source in series with a resistance (Correct answer)
- A current source in parallel with a resistance
- Two resistors in series
- A capacitor and resistor in parallel
Correct answer: A voltage source in series with a resistance
Thevenin's theorem reduces any linear two-terminal network to a single voltage source (Vth) in series with a resistance (Rth).
Question 2: What is the conductance of a 25Ω resistor?
- 0.04 S (Correct answer)
- 25 S
- 0.4 S
- 4 S
Correct answer: 0.04 S
Conductance G = 1/R = 1/25 = 0.04 siemens (S).
Question 3: A current of 3A flows through a 4Ω resistor for 10 seconds. How much energy is dissipated?
- 360 J (Correct answer)
- 120 J
- 36 J
- 1200 J
Correct answer: 360 J
Energy W = P × t = I²Rt = 3² × 4 × 10 = 9 × 4 × 10 = 360 J.
Question 4: Norton's theorem converts a network to which equivalent?
- A current source in parallel with a resistance (Correct answer)
- A voltage source in series with a resistance
- Two current sources in parallel
- A resistor and capacitor in series
Correct answer: A current source in parallel with a resistance
Norton's equivalent circuit consists of a short-circuit current source (In) in parallel with the Norton resistance (Rn).
Question 5: In a current divider with two parallel resistors R1=4Ω and R2=12Ω and total current IT=8A, what current flows through R1?
- 6A (Correct answer)
- 2A
- 4A
- 8A
Correct answer: 6A
I1 = IT × R2/(R1+R2) = 8 × 12/(4+12) = 8 × 0.75 = 6A.
Question 6: The superposition theorem applies only to circuits that are:
- Linear and bilateral (Correct answer)
- Nonlinear and unilateral
- Purely resistive only
- DC only
Correct answer: Linear and bilateral
Superposition requires linearity (responses proportional to inputs) and works on bilateral circuits with multiple independent sources.
Question 7: Maximum power transfer from a source to a load occurs when load resistance equals:
- The source's internal (Thevenin) resistance (Correct answer)
- Zero ohms
- Twice the source resistance
- Infinite resistance
Correct answer: The source's internal (Thevenin) resistance
Maximum power transfer theorem states maximum power is delivered when RL = Rth (source internal resistance).
ISCET DC Circuits Fundamentals 3
Thevenin's theorem replaces a complex network with which equivalent circuit?