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This discussion item explores how grounding electrical components of an automobile to the frame results in electrical current flow. Learn about the purpose of grounding, the role of chassis ground, and the benefits it provides in automotive circuits.
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Current Flow in Automotive Circuits Class Discussion Item 2.9 Presenter: Derek Gilman Course: EAS 5407 Instructor: Dr. Ham
Question: How does grounding an electrical component of an automobile (ie. an alternator or starter motor) to the frame, result in an electrical current?
Background • Current is created when free electrons flow from the negative pole on a voltage source, (a battery in this case), to the positive pole. • By convention we consider current to be a positive flow in the opposite direction of the electron flow. • Chassis ground is the name given to the role performed by the frame of an automobile when it is connected to the electrical system.
Definition • Chassis Ground • A large conducting body used as a common return for an electric circuit and as an arbitrary zero of potential. Merriam-Webster Dictionary On-line
Purpose of Grounding • Grounding is done to prevent a floating voltage by determining a reference point for the circuit. • Chassis ground also serves as a connector between the battery and the electrical components.
Connection Car Battery + Alternator Chassis Ground
Closing the Circuit • Current flows from high potential to low potential in the circuit. • The battery’s negative pole is grounded to the chassis. • Current passes through loads en route to the chassis.
Why is it done this way? • Use of chassis ground simplifies circuit • Replaces wiring
Applied Knowledge • Car Jump-Start • Safety Feature in Instruments