BEE Electric Circuits 3 โ Questions and Answers
Question 1: In Thevenin's theorem, the Thevenin voltage (Vth) is defined as:
- The open-circuit voltage across the terminals of interest (Correct answer)
- The short-circuit current through the terminals
- The voltage across the internal resistance
- The Norton equivalent voltage
Correct answer: The open-circuit voltage across the terminals of interest
Vth is the open-circuit voltage measured across the terminals after removing the load.
Question 2: A sinusoidal current has a peak value of 14.14 A. What is its RMS value?
- 10 A (Correct answer)
- 14.14 A
- 7.07 A
- 20 A
Correct answer: 10 A
RMS value of a sinusoid = Peak / โ2 = 14.14 / 1.414 โ 10 A.
Question 3: Which circuit element opposes a change in current?
- Inductor (Correct answer)
- Resistor
- Capacitor
- Diode
Correct answer: Inductor
An inductor stores energy in a magnetic field and opposes changes in current through it.
Question 4: In the superposition theorem, when analyzing the contribution of one independent source, all other independent voltage sources are:
- Short-circuited (Correct answer)
- Open-circuited
- Left unchanged
- Replaced with their internal resistance
Correct answer: Short-circuited
Independent voltage sources not under analysis are replaced by short circuits (0 V) when applying superposition.
Question 5: What is the power factor of a purely inductive circuit?
- 0 (Correct answer)
- 1
- 0.5
- 0.707
Correct answer: 0
A purely inductive circuit has a 90ยฐ phase difference between voltage and current, giving a power factor of cos(90ยฐ) = 0.
Question 6: Norton's theorem replaces a complex network with a current source IN in parallel with:
- The Norton resistance RN (Correct answer)
- A voltage source
- An open circuit
- The Thevenin voltage
Correct answer: The Norton resistance RN
Norton's equivalent circuit consists of a current source IN in parallel with the equivalent resistance RN.
Question 7: What is the unit of inductance?
- Henry (H) (Correct answer)
- Farad (F)
- Ohm (ฮฉ)
- Weber (Wb)
Correct answer: Henry (H)
Inductance is measured in Henrys (H), where 1 H = 1 Vยทs/A.
BEE Electric Circuits 3
In Thevenin's theorem, the Thevenin voltage (Vth) is defined as: