ISCET DC Circuits Fundamentals 2 — Questions and Answers
Question 1: Three resistors of 10Ω, 20Ω, and 30Ω are connected in parallel. What is the equivalent resistance?
- 5.45Ω (Correct answer)
- 60Ω
- 20Ω
- 3.33Ω
Correct answer: 5.45Ω
For parallel resistors, 1/Req = 1/10 + 1/20 + 1/30 = 6/60 + 3/60 + 2/60 = 11/60, so Req ≈ 5.45Ω.
Question 2: A 12V battery with an internal resistance of 0.5Ω supplies current to a 5.5Ω external resistor. What is the terminal voltage?
- 11V (Correct answer)
- 12V
- 10V
- 6V
Correct answer: 11V
Current = 12V / (0.5 + 5.5) = 2A; terminal voltage = 12 - (2 × 0.5) = 11V.
Question 3: Which law states that the algebraic sum of all currents entering and leaving a node equals zero?
- Kirchhoff's Voltage Law
- Kirchhoff's Current Law (Correct answer)
- Ohm's Law
- Norton's Theorem
Correct answer: Kirchhoff's Current Law
Kirchhoff's Current Law (KCL) states that the sum of currents into a node equals the sum of currents out of the node.
Question 4: A circuit has a 24V source with two resistors in series: 6Ω and 18Ω. What is the voltage across the 18Ω resistor?
- 18V (Correct answer)
- 6V
- 12V
- 24V
Correct answer: 18V
Using the voltage divider: V18 = 24 × (18 / (6+18)) = 24 × 0.75 = 18V.
Question 5: What happens to total resistance when additional resistors are added in parallel to a circuit?
- Total resistance decreases (Correct answer)
- Total resistance increases
- Total resistance stays the same
- Total resistance doubles
Correct answer: Total resistance decreases
Adding parallel paths provides more routes for current flow, which always decreases total equivalent resistance.
Question 6: A 100Ω resistor dissipates 4W of power. What current flows through it?
- 0.2A (Correct answer)
- 0.04A
- 400A
- 2A
Correct answer: 0.2A
Using P = I²R, I = √(P/R) = √(4/100) = √0.04 = 0.2A.
Question 7: In a series circuit with a 9V battery and three equal resistors, each resistor drops which voltage?
- 3V (Correct answer)
- 9V
- 1V
- 27V
Correct answer: 3V
In a series circuit, voltage divides equally across identical resistors: 9V / 3 = 3V each.
ISCET DC Circuits Fundamentals 2
Three resistors of 10Ω, 20Ω, and 30Ω are connected in parallel.
What is the equivalent resistance?