Handbook 652 Body Electrical Diagnosis Voltage Drop Whenever current passes through any component (i.e., current is flowing), voltage is used up. The voltage used up is called voltage drop (ΔV). Δ is the Greek letter delta. The symbol delta means “change in.” When we use the abbreviation ΔV it indicates “change in voltage” or voltage drop. The voltage drop of a component is directly proportional to the resistance of the component. Low resistance components like fuses, switches, wires and connectors should have very low voltage drop. As a general rule the maximum voltage drop allowed for these components is less than 0.1V per component or connector in a body electrical circuit.
Higher resistance components are usually referred to as loads. Loads use their resistance to convert current into work (light, heat, motion). This conversion causes voltage drop as the electrical pressure is used up. Typical loads include lamps, motors, relay coils and most sensors. When loads are in series, each component ’ s voltage drop is proportional to its resistance. The higher the resistance, the higher the ΔV. In any electrical circuit, all the voltage is always used up. Adding up all the voltage drops in a circuit always equals source voltage. 20 Technical Training