EIT Electrical Circuits 2 — Questions and Answers
Question 1: In an AC circuit, inductive reactance X_L is calculated as:
- 1/(2πfC)
- 2πfL (Correct answer)
- R + jX
- V/I
Correct answer: 2πfL
Inductive reactance X_L = 2πfL = ωL, where f is frequency and L is inductance in henries.
Question 2: What theorem states that any linear two-terminal circuit can be replaced by a single voltage source and series resistance?
- Norton's Theorem
- Superposition Theorem
- Thevenin's Theorem (Correct answer)
- Maximum Power Transfer Theorem
Correct answer: Thevenin's Theorem
Thevenin's Theorem simplifies complex networks to a voltage source V_th in series with resistance R_th.
Question 3: At resonance in a series RLC circuit, the impedance is:
- Maximum
- Minimum (equal to R) (Correct answer)
- Zero
- Infinite
Correct answer: Minimum (equal to R)
At resonance, inductive and capacitive reactances cancel (X_L = X_C), leaving only resistance, so Z is minimum and equal to R.
Question 4: What is the phase relationship between voltage and current in a pure inductor?
- In phase
- Voltage leads current by 90° (Correct answer)
- Current leads voltage by 90°
- 180° out of phase
Correct answer: Voltage leads current by 90°
In a pure inductor, voltage leads current by 90° (π/2 radians) because V = L(dI/dt).
Question 5: The turns ratio of a transformer is 10:1 (primary:secondary). If the primary voltage is 120V, what is the secondary voltage?
- 1200 V
- 12 V (Correct answer)
- 120 V
- 240 V
Correct answer: 12 V
V_s/V_p = N_s/N_p → V_s = 120 × (1/10) = 12 V.
Question 6: Which circuit element opposes changes in voltage?
- Resistor
- Inductor
- Capacitor (Correct answer)
- Diode
Correct answer: Capacitor
A capacitor stores energy in an electric field and opposes changes in voltage because V = Q/C and charge takes time to accumulate.
EIT Electrical Circuits 2
In an AC circuit, inductive reactance X_L is calculated as: