In this article, electrical engineer, Jim Orosz, P.E., provides an introduction to the basics of electricity. He discusses voltage, resistance, current, and how each variable affects the injury potential in electrical shock cases.
Electricity Basics: Voltage, Resistance & Current
In the modern world we have come to rely on electricity; it is used to heat our homes, prepare our meals, and drive the productivity of industry, yet the fundamentals of electricity remain a mystery in the minds of many. This lack of clarity poses a real challenge when attempting to convey complex information to the fact finders when electrical matters are at the heart of a legal dispute.
In my experience testifying as an Electrical Engineer, I often find that people outside of the industry struggle to discuss the basic principles of the discipline. Terms such as Volts, Ohms, and Amps can be very confusing for the fact finder and must be presented in a way that is clearly understood. The solution is to provide a foundation of knowledge upon which more complex information can be built.
Electricity as a Dam
Voltage – Is like the water building behind the dam. The level of the water represents the potential energy (potential difference). The higher the level of water (Voltage), the higher the potential power when it is released.
Resistance – Can be represented by a hole in the dam. The higher the Resistance (the smaller the hole), the less water (Current) that can pass through. The lower the Resistance (the larger the hole), the more water (Current) that can pass through.
Current – The amount of water flowing through the hole. This is a product of the water level (Voltage) and the hole in the dam (Resistance).
Electrical Shock Injuries
Between Voltage, Resistance and Current, the electric Current (measured in Amps) is the most important variable in determining the potential severity of an electrical shock hazard. The table below illustrates the relationship between these variables. In the final column we have provided OSHA data on the physiological effects of electrical Currents on the human body.
In addition to the Amperage of the electrical Current there are a number of factors that will influence the severity of an electrical shock; of particular importance are:
- the path which the electrical current flows through the body and
- the electrical Resistance of the body.
These aspects vary widely dependent on site specific factors and may represent the difference between life and death for the injured parties.
Investigating Electrical Shock Injuries
The electrical engineers at Robson Forensic regularly investigate electrical shock injuries and electrocutions to determine their cause. These investigations typically include an evaluation for the presence of defects, the adequacy of warnings and instructions, and user actions.
As a Major in the U.S. Army Reserve, working with FEMA on disaster relief, a West Point graduate in electrical engineering, and an accomplished Professional Engineer in the private sector, Jim is uniquely qualified to investigate electrical safety matters.
For more than ten years Jim worked in engineering and engineering management positions with Consolidated Edison Incorporated. During this time he was responsible for the safety and reliability of the electrical power distribution system, which included conducting inspections of the distribution system, development of test specifications for underground cables, and managing maintenance on the network.
In addition to his experience with electrical utilities, Jim worked as a supervisor of maintenance, operations, and safety for General Motors; he also served in a variety of functions with the United States Army Corps of Engineers. In these roles Jim gained extensive practical experience with industrial and heavy equipment.
Several members of the electrical engineering practice group regularly investigate electrical shock incidents. Please contact Robson Forensic to discuss your case and determine which of our experts is best qualified to assist with the specific issues in your case.