In electronics, voltage drop is the decrease of electric potential along the path of a current flowing in a circuit.
Voltage drops in the internal resistance of the source, across conductors, across contacts, and across connectors are undesirable because some of the energy supplied is dissipated.
An excessive voltage drop may result in the unsatisfactory performance of the space heater and the overheating of the wires and connections.
The simplest way to reduce voltage drop is to increase the diameter of the conductor between the source and the load, which lowers the overall resistance.
The DC source, the conductors (wires), the resistors, and the light bulb (the load) all have resistance; all use and dissipate supplied energy to some degree.
Analogous to Ohm's law for direct-current circuits, electrical impedance may be expressed by the formula E = I Z.