CET DC Circuit Analysis & Theory 3 — Questions and Answers
Question 1: Three resistors of 6 Ω, 12 Ω, and 4 Ω are connected in parallel. What is the equivalent resistance?
- 22 Ω
- 2 Ω (Correct answer)
- 11 Ω
- 7 Ω
Correct answer: 2 Ω
1/R = 1/6 + 1/12 + 1/4 = 2/12 + 1/12 + 3/12 = 6/12; R = 2 Ω.
Question 2: Kirchhoff's Current Law states that the sum of currents entering a node equals:
- Zero
- The supply voltage
- The sum of currents leaving the node (Correct answer)
- The total resistance
Correct answer: The sum of currents leaving the node
KCL is based on conservation of charge: current in = current out at any node.
Question 3: In a parallel circuit with a 24 V source and branch resistors of 8 Ω and 12 Ω, what is the total current supplied by the source?
- 1 A
- 2 A
- 5 A (Correct answer)
- 7 A
Correct answer: 5 A
I1 = 24/8 = 3 A; I2 = 24/12 = 2 A; total = 5 A.
Question 4: A current divider has two parallel resistors, R1 = 10 Ω and R2 = 40 Ω. If total current is 5 A, how much flows through R1?
- 1 A
- 2 A
- 4 A (Correct answer)
- 5 A
Correct answer: 4 A
I1 = I_total × R2/(R1+R2) = 5 × 40/50 = 4 A.
Question 5: Which of the following best describes a short circuit condition in a DC network?
- Very high resistance path between two nodes
- Zero resistance path between two nodes (Correct answer)
- Open path with no current flow
- A path with exactly 1 Ω resistance
Correct answer: Zero resistance path between two nodes
A short circuit provides a near-zero resistance path, causing maximum (potentially damaging) current flow.
Question 6: If the voltage across a parallel combination is 12 V and one branch draws 0.3 A while another draws 0.5 A, what is the total power consumed?
- 3.6 W
- 6 W
- 9.6 W (Correct answer)
- 12 W
Correct answer: 9.6 W
Total current = 0.8 A; P = V × I = 12 × 0.8 = 9.6 W.
Question 7: Which statement about parallel circuits is correct?
- Current is the same in all branches
- Voltage is the same across all branches (Correct answer)
- Resistance increases as more branches are added
- Opening one branch increases current in others
Correct answer: Voltage is the same across all branches
In a parallel circuit, every branch is directly connected to the source, so each branch has the same terminal voltage.
CET DC Circuit Analysis & Theory 3
Three resistors of 6 Ω, 12 Ω, and 4 Ω are connected in parallel.
What is the equivalent resistance?