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SECTION 1: ELECTRICAL THEORY & OHM'S LAW
Question 1
According to Ohm's Law, if a circuit has a voltage of 120 volts and a resistance of 30
ohms, what is the current flow in amperes?
A) 2 A
B) 4 A
C) 6 A
D) 8 A
Correct Answer: B) 4 A
*Explanation: Ohm's Law states I = E/R; 120V ÷ 30Ω = 4 amperes. This fundamental
calculation is essential for sizing conductors, selecting overcurrent protection, and
troubleshooting electrical circuits in municipal facilities .*
Question 2
Ohm's Law is expressed as:
A) P = VI
B) V = IR
C) I = PR
D) V = PI
Correct Answer: B) V = IR
,Explanation: Ohm's Law defines the relationship between voltage (V), current (I), and
resistance (R): V = I × R. The other formulas are power-related (P = VI is the power
formula) .
Question 3
A 10Ω resistor carries 2A current. What is the voltage across it?
A) 5V
B) 12V
C) 18V
D) 20V
Correct Answer: D) 20V
*Explanation: Using Ohm's Law: V = I × R = 2A × 10Ω = 20 volts .*
Question 4
What is the unit of electrical resistance?
A) Volt
B) Ampere
C) Ohm
D) Watt
Correct Answer: C) Ohm
Explanation: The ohm (Ω) is the SI unit of electrical resistance. Volts measure voltage
(potential difference), amperes measure current (flow rate), and watts measure power
(work rate) .
Question 5
What is the unit of electric power?
,A) Volt
B) Ampere
C) Ohm
D) Watt
Correct Answer: D) Watt
Explanation: The watt is the SI unit of electrical power. One watt equals one joule per
second. Power calculations use P = V × I (for DC) or P = V × I × Power Factor (for AC) .
Question 6
A 240V single-phase load draws 18A. What is the power consumption?
A) 2.16 kW
B) 4.32 kW
C) 5.10 kW
D) 3.60 kW
Correct Answer: B) 4.32 kW
*Explanation: Using P = V × I, 240V × 18A = 4320W = 4.32 kW. This formula is
fundamental for determining load requirements and service sizing .*
Question 7
What is the formula for calculating electrical power (P) in a DC circuit? (Select all that
apply)
A) P = I × R
B) P = V × I
C) P = V² / R
D) P = I² × R
Correct Answers: B, C, D
, Explanation: Power in DC circuits can be calculated using P = V × I (voltage times
current). By substituting Ohm's Law (V = I × R), the other equivalent formulas are P = V² /
R and P = I² × R. Option A (P = I × R) is dimensionally inconsistent and incorrect .
Question 8
In a DC circuit, current flows:
A) Alternating direction
B) Only in one direction
C) Randomly
D) Only in transformers
Correct Answer: B) Only in one direction
Explanation: Direct current (DC) is unidirectional—it flows in only one direction.
Alternating current (AC) reverses direction periodically. Batteries and solar panels produce
DC; utility power is AC .
Question 9
In an AC circuit, current flows:
A) In one direction only
B) Periodically reverses direction
C) Randomly
D) Only when a capacitor is present
Correct Answer: B) Periodically reverses direction
Explanation: Alternating current (AC) periodically reverses direction. In the US, standard
frequency is 60 Hz, meaning the current changes direction 120 times per second (60
complete cycles) .