BMST Electrical Circuits and Ohm's Law 4 — Questions and Answers
Question 1: A 60 W light bulb operates at 120 V. What is its resistance?
- 2 Ω
- 72 Ω
- 240 Ω (Correct answer)
- 720 Ω
Correct answer: 240 Ω
Using P = V²/R, R = V²/P = 14400/60 = 240 Ω.
Question 2: In a series circuit, which quantity remains the same throughout?
- Voltage
- Current (Correct answer)
- Resistance
- Power
Correct answer: Current
In a series circuit, the same current flows through every component since there is only one path.
Question 3: What is the voltage drop across a 15 Ω resistor when 3 A flows through it?
- 5 V
- 18 V
- 45 V (Correct answer)
- 90 V
Correct answer: 45 V
V = IR = 3 × 15 = 45 V.
Question 4: Which material is the best conductor of electricity?
- Rubber
- Glass
- Copper (Correct answer)
- Wood
Correct answer: Copper
Copper is an excellent conductor with very low electrical resistance, making it widely used in wiring.
Question 5: A circuit has a 12 V source and three equal resistors in series drawing 0.5 A. What is each resistor's value?
- 4 Ω
- 6 Ω
- 8 Ω (Correct answer)
- 12 Ω
Correct answer: 8 Ω
Total R = V/I = 12/0.5 = 24 Ω; each of three equal resistors = 24/3 = 8 Ω.
Question 6: What does Kirchhoff's Voltage Law (KVL) state?
- Current at a junction is conserved
- The sum of voltage drops around a closed loop equals the source voltage (Correct answer)
- Resistance is proportional to length
- Power equals current squared times resistance
Correct answer: The sum of voltage drops around a closed loop equals the source voltage
KVL states that the algebraic sum of all voltages around any closed loop in a circuit equals zero.
Question 7: If a resistor's resistance doubles and the voltage across it stays the same, what happens to current?
- Current doubles
- Current halves (Correct answer)
- Current quadruples
- Current stays the same
Correct answer: Current halves
By Ohm's Law, I = V/R; doubling R with constant V cuts the current in half.
BMST Electrical Circuits and Ohm's Law 4
A 60 W light bulb operates at 120 V.
What is its resistance?