BEE - Bachelor of Electrical Engineering Circuit Analysis 1 — Questions and Answers
Question 1: Thevenin's theorem states that any linear circuit with sources and resistors can be replaced by:
- A single current source in parallel with a resistance
- A single voltage source in series with a resistance (Correct answer)
- Two voltage sources connected in series
- A single resistor connected to ground
Correct answer: A single voltage source in series with a resistance
Thevenin's theorem simplifies any linear two-terminal network into an equivalent circuit consisting of a single ideal voltage source (Vth) in series with a single resistance (Rth), making complex circuit analysis much simpler.
Question 2: In a voltage divider with resistors R1 and R2 in series across a supply voltage Vs, the voltage across R2 is:
- Vs × (R1 / (R1 + R2))
- Vs × (R2 / (R1 + R2)) (Correct answer)
- Vs × (R1 + R2) / R2
- Vs × R1 × R2
Correct answer: Vs × (R2 / (R1 + R2))
The voltage divider rule states that the voltage across any resistor in a series string equals the total voltage multiplied by that resistor's value divided by the total series resistance. Vout = Vs × R2/(R1+R2).
Question 3: The superposition theorem is applicable only to circuits that are:
- Non-linear and time-variant
- Linear and bilateral (Correct answer)
- Purely resistive with no sources
- Resonant at a specific frequency
Correct answer: Linear and bilateral
The superposition theorem requires the circuit to be linear (obeying proportionality) and bilateral (element behavior is the same in both directions of current flow). It allows each independent source to be analyzed separately, then results summed.
Question 4: In mesh analysis, which law is applied to write the equations for each mesh?
- Kirchhoff's Current Law
- Norton's theorem
- Kirchhoff's Voltage Law (Correct answer)
- Thevenin's theorem
Correct answer: Kirchhoff's Voltage Law
Mesh analysis applies Kirchhoff's Voltage Law (KVL) around each independent loop (mesh) in the circuit. The sum of all voltage rises and drops around a closed loop equals zero, giving one equation per mesh.
Question 5: A purely inductive circuit carrying a sinusoidal current has a power factor of:
- 1
- 0.5
- 0.707
- 0 (Correct answer)
Correct answer: 0
In a purely inductive circuit, current lags voltage by 90°. Power factor equals cos(90°) = 0, meaning no real (active) power is consumed — only reactive power is exchanged between the source and the inductor.
Question 6: Norton's equivalent circuit consists of:
- A voltage source in series with an impedance
- A current source in parallel with a resistance (Correct answer)
- Two current sources in series
- A resistor in series with a capacitor
Correct answer: A current source in parallel with a resistance
Norton's theorem represents any linear two-terminal network as an ideal current source (IN) in parallel with a resistance (RN). Norton's and Thevenin's equivalents are interchangeable: IN = Vth/Rth and RN = Rth.
BEE - Bachelor of Electrical Engineering Circuit Analysis 1
Thevenin's theorem states that any linear circuit with sources and resistors can be replaced by: