PC Electrical Theory & Principles 3 — Questions and Answers
Question 1: Three resistors of 6Ω, 12Ω, and 4Ω are connected in parallel. What is the total equivalent resistance?
- 22Ω
- 2Ω (Correct answer)
- 7.3Ω
- 0.5Ω
Correct answer: 2Ω
1/Rt = 1/6 + 1/12 + 1/4 = 2/12 + 1/12 + 3/12 = 6/12; Rt = 2Ω.
Question 2: In a parallel circuit, which quantity remains the same across all branches?
- Current
- Resistance
- Voltage (Correct answer)
- Power
Correct answer: Voltage
Voltage is identical across all branches in a parallel circuit.
Question 3: Kirchhoff's Current Law (KCL) states that:
- Current is the same in all branches
- The sum of currents entering a node equals the sum leaving it (Correct answer)
- Total current equals source voltage divided by largest resistance
- Current increases at each branch junction
Correct answer: The sum of currents entering a node equals the sum leaving it
KCL states that the algebraic sum of all currents at any node equals zero — what enters must leave.
Question 4: A capacitor in a DC circuit, after fully charging, acts like a(n):
- Short circuit
- Open circuit (Correct answer)
- Low-value resistor
- Inductor
Correct answer: Open circuit
A fully charged capacitor blocks DC current, effectively acting as an open circuit.
Question 5: Capacitance is measured in which unit?
- Henry (H)
- Ohm (Ω)
- Farad (F) (Correct answer)
- Siemens (S)
Correct answer: Farad (F)
Capacitance is measured in Farads (F), with practical values often in microfarads (µF) or picofarads (pF).
Question 6: When capacitors are connected in series, the total capacitance compared to the smallest individual capacitor is:
- Greater
- Equal
- Less (Correct answer)
- Doubled
Correct answer: Less
Series capacitors reduce total capacitance below the smallest individual value, opposite to resistors in series.
Question 7: An inductor opposes changes in which electrical quantity?
- Voltage
- Resistance
- Current (Correct answer)
- Frequency
Correct answer: Current
Inductors oppose changes in current by generating a back-EMF proportional to the rate of current change.
PC Electrical Theory & Principles 3
Three resistors of 6Ω, 12Ω, and 4Ω are connected in parallel.
What is the total equivalent resistance?