G18-N G18 Residential Electrician Exam
Question 1 Which law expresses the relationship between voltage, current, and resistance in an electrical circuit?
- Coulomb’s Law
- Ohm’s Law
- Watt’s Law
- Faraday’s Law
Correct Answer: B
Explanation: Ohm’s Law states that V = I × R, describing the relationship between voltage, current, and resistance.
Question 2 In a DC circuit, if the voltage remains constant but the resistance doubles, what happens to the current?
- It halves
- It remains the same
- It doubles
- It becomes zero
Correct Answer: A 1 / 4
G18-N G18 Residential Electrician Exam
Explanation: According to Ohm’s Law, current (I) is inversely proportional to resistance (R) if voltage is constant.
Question 3 Which of the following is the correct expression for electrical power in terms of voltage and current?
A) P = V + I
B) P = V / I
C) P = V × I
D) P = V² / I
Correct Answer: C
Explanation: Electrical power is calculated as P = V × I, where V is voltage and I is current.
Question 4 In a purely resistive AC circuit, the voltage and current are
- in phase
- 90° out of phase
- 180° out of phase
- in resonance
- / 4
G18-N G18 Residential Electrician Exam
Correct Answer: A
Explanation: In a purely resistive circuit, voltage and current reach their peaks simultaneously, making them in phase.
Question 5 Which statement best describes alternating current (AC) in residential wiring?
- The current flows in only one direction
- The polarity remains the same at all times
- The current periodically reverses direction
- The voltage is always constant
Correct Answer: C
Explanation: AC power repeatedly reverses direction, changing polarity at a specific frequency (often 60 Hz in residential systems).
Question 6 What is the frequency of AC power most commonly supplied to residential homes in the United States?
- 50 Hz
- 60 Hz
- 100 Hz 3 / 4
G18-N G18 Residential Electrician Exam
- 120 Hz
Correct Answer: B
Explanation: In the US, the standard frequency for residential electrical supply is 60 cycles per second (60 Hz).
Question 7 A circuit has a current of 5 A and a resistance of 4 Ω. What is the voltage across it?
A) 1 V
B) 20 V
C) 9 V
D) 60 V
Correct Answer: B
Explanation: Using Ohm’s Law, V = I × R = 5 A × 4 Ω = 20 V.
Question 8 In a series circuit, the current throughout each component is
- different at each component
- the same through all components
- half of the total supply current
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