CSLB C-10 Electrical ContractorElectrical Theory and CalculationsEasy
A client has a 120V circuit supplying a load that draws 10 amps. If the total resistance of the conductors in the circuit is 0.5 ohms, what is the voltage drop across the conductors?
- A2.5V
- B10V
- C5V
- D12V
Show answer & explanationAnswer & explanation
Correct answer: C. 5V
Voltage drop (Vd) is calculated using Ohm's Law: Vd = I * R, where I is the current and R is the resistance of the conductors.
Why the other options are wrong
- A. This is a calculation error, possibly dividing by 2 instead of multiplying.
- B. This is a calculation error, possibly using an incorrect resistance value.
- D. This is a calculation error, possibly confusing it with percentage drop.
Voltage Drop (Ohm's Law)
Voltage drop is the reduction in electrical potential along the length of a conductor due to its resistance. It is calculated using Ohm's Law (V = I * R).
- Calculated as Vd = I * Rconductor.
- High voltage drop leads to reduced efficiency and performance.
- NEC limits maximum permissible voltage drop for feeders and branch circuits.
Memory trick: Voltage 'Drops' when Current 'Runs' through Resistance.