Lineman Electrical Theory and Principles 1 — Questions and Answers
Question 1: According to Ohm's Law, if a circuit has a voltage of 120V and a resistance of 30 ohms, what is the current?
- 2 amps
- 4 amps (Correct answer)
- 6 amps
- 8 amps
Correct answer: 4 amps
Ohm's Law states I = V/R, so 120V ÷ 30Ω = 4 amps.
Question 2: What is the standard frequency of AC power in the United States?
- 25 Hz
- 50 Hz
- 60 Hz (Correct answer)
- 120 Hz
Correct answer: 60 Hz
The US power grid operates at 60 Hz, meaning the current alternates direction 60 times per second.
Question 3: Which of the following best describes power factor in an AC circuit?
- The ratio of true power to apparent power (Correct answer)
- The ratio of voltage to current
- The resistance of the load in ohms
- The phase angle in radians
Correct answer: The ratio of true power to apparent power
Power factor is the ratio of real (true) power (watts) to apparent power (volt-amperes), ranging from 0 to 1.
Question 4: In a series circuit, if one component fails (opens), what happens to the rest of the circuit?
- Current increases in remaining components
- The entire circuit stops conducting (Correct answer)
- Voltage drops to zero across all components
- Remaining components share the missing load
Correct answer: The entire circuit stops conducting
In a series circuit, all components share the same current path, so an open in any one component interrupts current flow through the entire circuit.
Question 5: What is the relationship between frequency and period of an AC waveform?
- Period = Frequency × 2π
- Period = 1 / Frequency (Correct answer)
- Frequency = Period × 60
- Period = Frequency²
Correct answer: Period = 1 / Frequency
Period (T) is the time for one complete cycle, and it equals 1 divided by frequency (f), expressed as T = 1/f.
Question 6: Which unit is used to measure electrical resistance?
- Farad
- Henry
- Ohm (Correct answer)
- Siemens
Correct answer: Ohm
Resistance is measured in ohms (Ω), named after Georg Simon Ohm who formulated the relationship between voltage, current, and resistance.
Question 7: In a parallel circuit, the total resistance is always:
- Greater than the largest individual resistance
- Equal to the sum of all resistances
- Less than the smallest individual resistance (Correct answer)
- Equal to the average of all resistances
Correct answer: Less than the smallest individual resistance
In a parallel circuit, adding more paths for current flow reduces total resistance below that of any single branch.
Lineman Electrical Theory and Principles 1
According to Ohm's Law, if a circuit has a voltage of 120V and a resistance of 30 ohms, what is the current?