Mechanical Aptitude Mechanical Aptitude Basic Electrical Circuits 4 — Questions and Answers
Question 1: Which type of circuit breaker characteristic makes it suitable for protecting motors against startup current surges?
- Standard breaker
- Time-delay (slow-blow) breaker (Correct answer)
- Instantaneous breaker
- Ground-fault breaker
Correct answer: Time-delay (slow-blow) breaker
Time-delay breakers tolerate brief current surges like motor startup without tripping, while still protecting against sustained overloads.
Question 2: In a parallel circuit with a 24V source and two resistors (6 ohms and 12 ohms), what is the total current from the source?
- 2 amps
- 4 amps
- 6 amps (Correct answer)
- 12 amps
Correct answer: 6 amps
Current through 6Ω = 24/6 = 4A; current through 12Ω = 24/12 = 2A; total = 4 + 2 = 6 amps.
Question 3: What does a 'ground' connection in an electrical circuit primarily provide?
- Increased voltage to the circuit
- A safe return path and protection against shock (Correct answer)
- Higher current capacity for the circuit
- Improved signal quality only
Correct answer: A safe return path and protection against shock
Grounding provides a low-resistance path to earth that protects people from electrical shock if insulation fails.
Question 4: How much energy (in watt-hours) does a 100-watt light bulb consume if left on for 8 hours?
- 12.5 watt-hours
- 108 watt-hours
- 800 watt-hours (Correct answer)
- 0.8 watt-hours
Correct answer: 800 watt-hours
Energy = Power × Time = 100W × 8h = 800 watt-hours.
Question 5: What is the function of a capacitor in an electrical circuit?
- It converts AC to DC
- It increases resistance proportionally
- It stores and releases electrical energy (Correct answer)
- It steps up voltage permanently
Correct answer: It stores and releases electrical energy
A capacitor stores electrical energy in an electric field between two conductive plates and can release that energy back into the circuit.
Question 6: If a 60-watt bulb and a 100-watt bulb are connected in series across 120V, which bulb glows brighter?
- The 100-watt bulb
- The 60-watt bulb (Correct answer)
- Both glow equally bright
- Neither glows — the circuit fails
Correct answer: The 60-watt bulb
The 60-watt bulb has higher resistance (at rated voltage), and in series, more resistance means more voltage drop and more power dissipated in that component.
Question 7: What is the SI unit of electrical charge?
- Ampere
- Volt
- Coulomb (Correct answer)
- Farad
Correct answer: Coulomb
The coulomb is the SI unit of electric charge; one coulomb equals the charge transferred by one ampere flowing for one second.
Mechanical Aptitude Mechanical Aptitude Basic Electrical Circuits 4
Which type of circuit breaker characteristic makes it suitable for protecting motors against startup current surges?