Electrical units

Electrical Units are uniform across both metric and Imperial systems. You’ll need to know basic electrical concepts to determine electric loads, measure galvanic reactions and battery performance, and select the correct type of wiring and connections for vehicle electrical systems.

Basic electrical measurements

• Volts (V) are the measurement of Electromotive Force (EMF or E).
• Amperes (A) is the measurement of Electrical Current Flow Rate (I).
• Ohm (Ω) is the measurement of Electrical Load or Resistance (R).
• Watts (W) is the measurement of Power (P).

All these measurements are defined by Ohm’s Law, which states that current flow in a circuit varies in direct proportion to changes in voltage, and in inverse proportion to changes in resistance. This is expressed in the equation:

• E = I x R or V = A x Ω

Electrical power is the product of Electromotive Force and current Flow. This is expressed as:

• P = I x E or W = A x V