Chapter 2. Electricity and Electrical. Safety

Transcription

1 Chapter 2 Electricity and Electrical Safety

2 Understanding Electricity

3 Have you ever tried to define the word Electricity? It is not an easy task because electricity is not tangible. It can not be observed, placed on your mantle or shown to a friend. Electricity is an event or occurrence rather than an object. Electricity is probably best described as energy that results from the movement of electrons in an orderly manner. This movement is described as an electric current.

4 The interesting thing is that when the electrons move there is a void or hole left behind. Therefore electricity could also be accurately described as energy created by this movement of holes.

5 Understanding Electrical Terms and Measurements

6 Electrical Units of Measurement There are several units of measurement relating to electricity. For the purpose of understanding basic electricity you will learn the following measurements: Amperage Voltage Ohms

7 Amperage As mentioned, an electrical current describes the movement of electrons or the void of electrons (commonly called holes). Current is measured by determining the number of electrons or holes passing a single point in one second.

8 Amperage Since an extraordinary number of electrons or holes can pass a single point in one second, it is incomprehensible and impractical to calculate using the number of electrons. It is easier to use a measurement called a coulomb.

9 Amperage A coulomb is equal to approximately 6,240,000,000,000,000,000 electrons or holes. If this same number of electrons passes through a given point in exactly one second the measurement is referred to as an ampere or what is commonly referred to as an Amp. An ampere is the standard unit of electric current.

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11 Voltage The movement of electrons described earlier can only occur if there is a vacancy of electrons in one area and an excess of electrons in an adjacent area. This tension created between the two areas is called an Electromotive Force (EMF). This force is measured by a unit called volts.

12 Voltage Voltage is often described as the potential Electromotive Force as current does not have to be flowing between the two areas for there to be voltage.

13 Ohms Ohms refers to resistance. Any movement of electrons can be affected by resistance. Having resistance will limit the amount of electrons passing through a specific point over a specific period of time. The higher the resistance, the less electrons or holes that will be able to move over a specific period of time. The less resistance, the more electrons or holes that can move over a specific period of time.

14 Ohms Law Ohms Law refers to the interaction between Amperage, Voltage and Ohms. The relationship is described by the equation: Voltage = Amps x Ohms

15 Explaining Electricity to Your Students by Using the Electricity Water Analogy

16 Electricity / Water Analogy For those unfamiliar with basic electrical concepts, most find them easier to understand if a parallel can be drawn to something more familiar. Most electrical engineers use the Electricity / Water Analogy to help explain the concepts to non electrically educated people.

17 Electricity vs Water Battery Pool / Pump Volts Pressure Amps Water Flow Ohms Friction Conductor Pipes Electrons Water

18 Battery Pool / Pump The first analogy is that the battery is like a pool and pump. The battery supplies an electrical charge into the circuit. When the battery is dead it no longer contains a charge. The pool and pump supplies water into water pipes. When the pool is empty it will no longer pump water into the pipes.

19 Volts Pressure The second analogy compares volts to water pressure in the water pipes. Electrical pressure is referred to as the Electromotive Force (EMF). This pressure is measured using volts. Water pressure is usually measured in pounds per square inch.

20 Amps Gallons per Minute The third analogy is that the water flow in pipes are similar to the flow of electrons in a conductor. Water flow in pipes is usually measured in gallons per minute. In other words, how many gallons pass a specific point in the pipes over the span of one minute. Electrical current is measured in amps. Amps measure the number of coulombs passing through a specific point in the conductor over one second.

21 Resistance Friction The fourth analogy compares Ohms to friction caused by the pipes. If the water pipes are narrow they will restrict the amount of water that flows through them. If the pipes also have semi blockage, the blockages will interfere with the waters ability to flow. Electrical circuits also have the ability to have the flow of electricity interfered with or restricted. This is referred to as resistance and is measured in Ohms.

22 Conductor Pipes The fifth analogy compares electrical conductors to water pipes. The wider, cleaner and stronger the water pipes, the easier water can pass through them. The more conductive a material is, the easier that electrons can flow through it.

23 Electrons Water The last analogy compares Electrons to Water. In an electrical circuit it is the flow of electrons that ultimately must occur for the circuit to be useful. In the same way, water must be pumped through the pipes before the energy from the pipes can be useful.

24 Factors That Effect the Severity of a Shock

25 Factors that effect the severity of the shock Voltage Amperage Contact Resistance Duration of Shock Skin Conditions Contact Duration Body Current Path / Distance Metabolic Acidosis Shock Location Secondary Injuries

26 Voltage High voltage electric shocks have the ability to penetrate the outer layer of skin thereby reducing resistance and increasing current flow. This allows more current to enter the body and increases the likelihood of burning.

27 The Shocknife delivers up to 7,500 volts at it s highest setting. This amount can be considered High Voltage. For safety reasons, the Shocknife circuit contains high resistance to lower the amount of amps that can be delivered into the body. So even though the voltage is high, the amperage remains extremely low.

28 Amperage The truth is that high amperage is far more dangerous than high voltage. This is because amperage involves the number of electrons that flow into the body tissue, where voltage involves the push of these electrons into the body. The combination of high amperage and high voltage is a fatal equation.

29 The Shocknife delivers less than 1 milliamp. That is less than 1/1000 of an amp. The most popular electromuscular disruption device used by police today uses more than 3X the level of amps and delivers it in a manner that allows the shock to flow through a greater area of the body.

30 The small gap space of the Shocknife prevents the flow of amperage into vital organs.

31 Contact Resistance The irony is that the more direct contact with the conducting material the lesser the observable burn trauma. If there is a gap space that allows larger arcing into the skin, it will actually increase the likely hood of observable burn trauma.

32 This is why it is important that trainees using the Shocknife deliver it in the same manner as a real knife. This means pressing the blade into the skin like they are trying to cut deep into the tissue. This will actually shrink the gap space and reduce the likelihood of any burn trauma.

33 Skin Conditions Perspiration on the skin can dramatically reduce skin surface resistance. In some cases it can reduce it up to a factor of 15 to 20 times the resistance of dry skin.

34 However, if the skin is covered with too much perspiration it can actually create a short on the blade of the Shocknife. This means that the perspiration covers the insulator gap between the electrodes. Since electricity always flows through the path of least resistance it will choose to flow directly through the perspiration instead of the skin of the participant.

35 Contact Duration Obviously the longer the shock is delivered to the same location on the body, the greater the likelihood of burn trauma. This is because the longer the exposure to the same location on the body, the greater the increase of heating in the surrounding tissue.

36 The estimated minimum current necessary to produce first-degree skin burns is 100 ma for a 1 second to 9 second exposure over a skin area of 1 sq cm.* The Shocknife produces less than 100 times this amount of current. *Mazer, Electrical Accident Investigation Handbook

37 GOAL FOR DURATION ON CONTACT = 0.5 Seconds With high voltage stun guns and similar products contact for up to 0.5 seconds will cause a person to be startled and repelled. One to 2 seconds of current discharge will cause the person to lose the ability to stand. Discharges of 3 to 5 seconds will leave the victim immobilized, dazed, and weak for five to fifteen minutes (Robinson 1990) Robinson, M.N., C.G. Brooks and G.D. Renshaw, Electric Shock Devices and Their Effects on the Human Body, Med. Sci. Law 30: (1990)

38 The Shocknife has less voltage and a smaller gap space than stunguns. For this reason the Shocknife will not have the same effect as stun guns. However, to ensure minimal possibility of injury Shocknife uses the same margins as given for stun guns. This means always trying to limit exposure to less than 1 second.

39 Bodily Current Path/Distance As stated earlier, electricity will always travel through the path of least resistance. The greater the distance the shock travels, the more area effected by the current. The path of the current will also raise or lower the injury potential from the shock. For example, if the path of the current flows through the heart, there is a greater risk than if it just flows through the skin.

40 Unlike devices designed to incapacitate that allow for current to flow through the body over great distances, the Shocknife only delivers a localized shock to the location of contact.

41 The distance between the electrodes is fixed at 1/8 inch in the SK-1 and ¼ inch in the Shocknife Max. This means it is almost impossible for the current to travel through the entire body and internal organs.

42 Metabolic Acidosis Metabolic Acidosis: An acidic state in the body in which excess acid is added to the body fluids or bicarbonate is lost from them. This can be caused in training by a build up of lactic acid from physical exertion which can lead to a state of metabolic acidosis.

43 Physical exertion of any kind can result in increased acid production from cell metabolism. This increased acidic presence can increase the severity of the shock.

44 Since the Shocknife is designed to be used during dynamic training, it is likely that trainees will exert themselves physically. This will result in the muscles experiencing some level of metabolic acidosis making their muscles more susceptible to current flow.

45 Secondary Injuries The reality is that more people are injured from secondary injuries during training than injuries from training tools. A secondary injury as a result of some other factor other than the tool being used in training. For example, a person recoils when shocked and hits their elbow on a fixed object.

46 It is the responsibility of all trainers to create the safest training environment possible. The environment must be free of sharp objects including corners of tables, etc. The floor should not have debris or be slippery. All appropriate safety gear should be worn at all times.

47 The location the shock is delivered will also effect injury potential. For example, shocks to the eyes, neck and testicles can cause injury directly from the shock.

48 1) Possible Carotid Sinus stimulation. 2) Possible unconsciousness from nerve plexus stimulation. Shocks to the neck must be avoided for two reasons: The Neck

49 Carotid Sinus Stimulation The Carotid Sinus is a barorecepter that sits at the bifurcation between the internal and external carotid arteries. It is an extension of the vagus nerve, which is responsible for the regulation of the heart beat. Stimulation of the Carotid Sinus can lower the heart rate and in some instances actually stop the heart from beating.

50 Although the Carotid Sinus is protected by the Sterniocladimastoid muscle, there is still a remote possibility that the Shocknife Shock may penetrate and stimulate the Carotid Sinus. For this reason alone the neck is a prohibited target when training with the Shocknife.

51 The second reason that the neck is a prohibited target when training with the Shocknife is because the sides of the neck contain two large nerve groups that are very sensitive to stimulation. Cervical and Brachial Plexus

52 The Cervical Plexus and Brachial Plexus Origin are both located on the sides of the neck. Stimulation to these points can cause momentary loss of cognitive functioning and in some instances unconsciousness.

53 Most trainers are familiar with the term Brachial Stun which describes a strike to the Brachial Plexus Origin with the hand or forearm. A shock delivered to the same location can cause the same results. The danger comes from secondary injuries resulting from loss of balance and/or falling.

54 Testicles A shock to the testicles carries the possibility of creating an injury referred to as testicular torsion. Testicular Torsion is described as rotation of the testicles that results in constriction of the spermatic cord that cuts of blood supply to the testicle, epididymis, and other structures. For this reason the Shocknife should NEVER be applied to the testicles of a trainee.

55 Eyes At no time should the Shocknife be used without eye protection that completely encases the eyes and surrounding area. Delivering a shock to the eyes can cause Electrothermal burns that can cause serious eye injuries and even blindness.

56 BURNING

57 Burning Unlike a burn that results from touching an externally hot object to flesh, an electrical burn is produced inside the tissue itself and is referred to as intrinsic in nature. These types of burns are referred to as Electrothermal burns. (Damjanov and Linder 1996) Damjanov, Ivan and James Linder, eds., Anderson s Pathology, 10th ed. (St. Louis: Mosby, 1996), 106.

58 The blade of the Shocknife can cause superficial inflammatory response (reddening of the top layer skin). Sometimes the skin will be slightly raised, but it usually flattens out without scarring. Most individuals that experience redness of the skin find it passes within a couple of hours. A small few report it took more than a day. However people with dark or tanned skin may find post inflammatory loss of pigment. (Frechette and Rimsza, 1992) Every person can have a different reaction to electrical shocks. There are individuals that have very sensitive skin and If a person is unsure how they will react they may choose not to participate in Shocknife training. In rare cases, individuals with very sensitive skin can have tissue damage, blistering and scarring. Frechette, A. and M.E. Rimsza, Stun Gun Injury: A New Presentation of the Battered Child Syndrome, Pediatrics 89(5); (1992)

59 Secondary Burning Secondary burning refers to burns caused by other material that has become ignited. Since the Shocknife blade presents a spark when activated, it has the ability to ignite flammable substances and gases. This is why it is imperative that training is conducted in a safe area free of flammable substances and gases.

60 Flammable Fabric Ensure that anyone training with the Shocknife are not wearing flammable fabric. Thin nylon clothing are susceptible to melting from the heat generated in the sparking. If you have any doubt as to whether the clothing is susceptible or not, test the clothing by rubbing the Shocknife over while it is not being worn. Ensure you use sufficient pressure.

61 You are now ready for the Chapter 2 quiz. Right click on this programs button on your computer s task bar and select close to end this lesson.