ISCET DC Circuits Fundamentals 5 — Questions and Answers
Question 1: What is the color code for a resistor with bands: brown, black, red, gold?
- 1kΩ ±5% (Correct answer)
- 102Ω ±10%
- 1002Ω ±5%
- 100Ω ±5%
Correct answer: 1kΩ ±5%
Brown=1, Black=0, Red=×100 multiplier, Gold=±5% tolerance: 10 × 100 = 1000Ω = 1kΩ ±5%.
Question 2: An open circuit condition in a series circuit causes:
- Zero current through the entire circuit (Correct answer)
- Maximum current through remaining components
- Voltage source to short out
- Equal voltage across all components
Correct answer: Zero current through the entire circuit
An open break in a series circuit stops all current flow since there is no complete path for current.
Question 3: What is the voltage across an open-circuit branch in a parallel circuit if the source is 15V?
- 15V (Correct answer)
- 0V
- 7.5V
- Infinite
Correct answer: 15V
All branches in a parallel circuit share the same voltage as the source; the open branch still has the full 15V across it.
Question 4: Doubling the length of a wire while keeping diameter constant will:
- Double its resistance (Correct answer)
- Halve its resistance
- Quadruple its resistance
- Have no effect on resistance
Correct answer: Double its resistance
Resistance R = ρL/A; doubling L while keeping A constant doubles resistance.
Question 5: Which of the following correctly states Kirchhoff's Voltage Law (KVL)?
- The sum of all voltage drops around a closed loop equals the sum of voltage sources (Correct answer)
- Current entering a node equals current leaving
- Power dissipated equals power supplied
- Voltage is constant in a parallel circuit
Correct answer: The sum of all voltage drops around a closed loop equals the sum of voltage sources
KVL states that the algebraic sum of all voltages around any closed loop is zero, meaning source EMFs equal the total of voltage drops.
Question 6: A 50V source drives current through a series circuit of 10Ω, 15Ω, and 25Ω. What is the voltage drop across the 15Ω resistor?
- 15V (Correct answer)
- 25V
- 10V
- 50V
Correct answer: 15V
I = 50/(10+15+25) = 50/50 = 1A; V15 = 1A × 15Ω = 15V.
Question 7: In a practical DC circuit, what is the purpose of a fuse?
- To open the circuit and protect against excessive current (Correct answer)
- To stabilize voltage during fluctuations
- To reduce resistance in the circuit
- To store energy for later use
Correct answer: To open the circuit and protect against excessive current
A fuse contains a metal element that melts and opens the circuit when current exceeds its rated value, protecting components from damage.
ISCET DC Circuits Fundamentals 5
What is the color code for a resistor with bands: brown, black, red, gold?