Voltage drop is the decrease of electric potential along the path of a current flowing in a circuit. It occurs due to the inherent resistance or impedance of wires carrying electricity, which causes a loss of voltage in the circuit. Voltage drop is particularly a problem with long cable runs, for example in larger buildings or on larger properties such as farms. National and local electrical codes may set guidelines for the maximum voltage drop allowed in electrical wiring to ensure efficiency of distribution and proper operation of electrical equipment. The maximum permitted voltage drop varies from one country to another.
To decrease the voltage drop in a circuit, one can increase the size (cross-section) of the conductors, which lowers the overall resistance. In power distribution systems, a given amount of power can be transmitted with less voltage drop if a higher voltage is used. More sophisticated techniques use active elements to compensate for excessive voltage drop.
The voltage drop formula is given by V = IZ, where V is the voltage drop, I is the current in amperes, and Z is the impedance in ohms. To check the voltage drop, use a voltmeter connected between the point where the voltage drop is to be measured. In DC circuits and AC resistive circuits, the total of all the voltage drops across series-connected loads should add up to the voltage applied to the circuit.
