Master Electrician Practice Exam

If a 90 ampere, 240-volt load is 225 feet away from a panelboard, what is the approximate voltage drop using 3 AWG copper conductors?

1. 5 volts

2. 10 volts

3. 15 volts

4. 20 volts

The correct answer is: 10 volts

To determine the approximate voltage drop for a 90 ampere, 240-volt load located 225 feet from a panelboard using 3 AWG copper conductors, one must use the formula for voltage drop in an electrical conductor: Voltage Drop (V) = 2 × Length (L) × Current (I) × Resistance per unit length (R) The resistance per unit length for 3 AWG copper wire is approximately 0.00328 ohms per foot. Given that the circuit is 225 feet long, the calculation for voltage drop would be as follows: 1. Calculate the total length of the circuit: since voltage drop occurs over both the outgoing and return paths, the total length is 2 × 225 feet = 450 feet. 2. Apply the values into the voltage drop formula: - Length = 450 feet - Current = 90 amperes - Resistance = 0.00328 ohms/foot Thus, the voltage drop can be calculated as: Voltage Drop = 2 × 225 × 90 × 0.00328 = approximately 10.5 volts. This value closely aligns with the choice of 10 volts, acknowledging potential variations due to rounding