Voltage drop across a conductor is calculated as which expression, and why is it important for socket and lighting circuits?

• A. Voltage drop is the product of current and resistance regardless of conductor length.
• B. Voltage drop equals current times resistance, but length is not involved.
• C. Voltage drop follows Ohm's law with resistance only, ignoring length.
• D. I × R × length per conductor; important to ensure voltage at the furthest point stays within limits.

Answer: (D)

Voltage drop is about how much the voltage falls from the supply to a point along a circuit when current flows through the conductor. The drop depends on the current and the resistance of the path, and since resistance increases with length, the total drop is found by multiplying the current by the total resistance of the conductor run. In practical terms, you can think of it as V_drop = I × R_run, and because R_run equals the resistance per unit length times the length, V_drop = I × (R_per_length × Length). This is why the expression that includes current, the conductor’s resistance, and the length is the correct way to calculate voltage drop. It’s important for socket and lighting circuits because you must keep the voltage at the farthest point within acceptable limits; otherwise lights may be dimmer and devices may not operate properly. This also guides selecting conductor size and route length to ensure the furthest outlet still receives adequate voltage.