Voltage Drop: Decrease in electric potential along a current's path in a circuit.
Undesirable in the internal resistance of sources, conductors, contacts, and connectors due to energy dissipation.
Voltage drop across load is related to power conversion efficiency.
Example Case
Space heater with 10 ohms resistance; wires supplying it have 0.2 ohms.
2% of total voltage lost in wires, affecting heater performance and causing wire overheating.
Regulation and Compensation
National/local electrical codes dictate maximum allowable voltage drop for efficiency and safety.
Techniques to reduce voltage drop:
Increase conductor diameter to reduce resistance.
Use higher voltage in power distribution systems.
Use active elements for compensation.
Resistive DC Voltage Drop
Calculated using Ohm's Law: V = IR.
Kirchhoff's Circuit Laws: Sum of voltage drops = supply voltage.
In a DC circuit with resistors in series:
Total circuit resistance affects voltage potential.
Larger resistors result in larger voltage drops.
Reactive AC Voltage Drop
AC Circuits: Include reactance as a type of opposition to current flow.
Impedance (Z): Sum of resistance and reactance, measured in ohms.
Impedance depends on frequency and conductor properties.
Voltage drop: E = IZ (analogous to Ohm's Law for DC).
Special Cases
PN Junctions in diodes/transistors have characteristic voltage drops when forward-biased.
Energy dissipated through photons, visible in LEDs.
Related Concepts
Brownout, Capacitive dropper, Electric power distribution, Electrical resistivity and conductivity, Ground loop, Kirchhoff's voltage law, Mesh analysis, Power cable, Voltage divider, Voltage droop.
References
"Voltage drop - maximum, determination, calculation of voltage drop", Schneider Electric.
"Electrical Principles for the Electrical Trades", Jim Jennesson, 5th edition.