1. Electricity. فيز 101 : محاضرة رقم 7: فيز 101 : محاضرة رقم 7: الكهرباء

2. Energy (ability to do work) & Matter (has physical form). The Universe is made up of Electricity is a some of Energy.

3. Hydrogen Oxygen Atoms

4. Hydrogen Oxygen

5. Conductor: Matter which supports electron flow. Metals – Salty Fluids – Human Body.

6. Insulator: Matter which does not support electron flow. In these substances the out electrons are rigidly held in place. Rubber – Glass – Wood.

7. Conductor carries the flow of electrons – current. Insulator prevents the conductor coming into contact with other Conductors (including people).

8. Some materials are half way between a Conductor and Insulator. We say they allow current to flow but offer some resistance. It’s a Conductor but its not a very good one. It resists the flow of electrons. Electrons release energy as they push their way through Such materials – examples the wire in the element of an electric fire. You can see it glow red hot when you switch on the fire and Electricity flows through the wire.

9. e_e_ e_e_ e_e_ e_e_ V Basic Circuit Theory

10. e_e_ e_e_ e_e_ e_e_ V Voltage is equivalent to pressure.

11. e_e_ e_e_ e_e_ e_e_ V Current is equivalent to flow.

12. Chemical Energy Electrical Energy Light Energy V = I.R Ohms Law. Voltage = Current x Resistance

13. Electricity is an efficient way to move energy around. The ESB turn the kinetic energy of the water moving in the Shannon into electrical energy – this is what a power station does. The electricity is piped (through copper wires) to the hospitals and home we live in. We then turn the electricity back into the form of energy we need either – light, or movement etc. Here is a simple explanation of what the ESB do.

14. ESB e_e_ e_e_ e_e_ e_e_ Hospital A+ Shannon River (source of Mechanical Energy)

15. ESB e_e_ e_e_ e_e_ e_e_ Hospital A+

16. ESB e_e_ e_e_ e_e_ e_e_ Hospital A+

17. ESB e_e_ e_e_ e_e_ Hospital A+

18. ESB e_e_ e_e_ Hospital A+

19. ESB e_e_ Hospital A+

20. ESB Hospital

21. ESB e_e_ e_e_ e_e_ e_e_ Hospital A+ e_e_ e_e_

22. ESB Hospital V = 220 I = V/R

23. ESB Hospital V = 220 I = V/R

24. ESB Hospital V = 220 I = V/R

25. ESB Hospital V = 220 I = V/R

26. Hospital G

27. Electrical Energy to………. Thermal Energy Mechanical Energy Radiation Energy Acoustic Energy Chemical Energy Kettle/heaters Food processor Light Bulb Hi-Fi Mobile Phone Battery Charger

28. If the insulators break down and you come in contact with the mains conductors then the current might flow down to ground through you giving you an electric shock. In fact the path of the current in through you, through the mass of the earth, and back to the transformer via capacitance. Nursing student do not need to be able to explain capacitance, but you Must be aware that the mains current will try and flow to ground, through you or your patients.

29. To protect from electric shock we add in an extra wire called the earth wire. Now if the insulation breaks down, the current will take the easy path back through the green wire, rather than going down through you. Normally current that flows if up to 13 amps. Its is limited by the resistance of the device you plug in. In the event of a break down in insulation, there is no resistance to limit the current and 100’s of amps can flow.

30. Fuse/MCB. Current limited by resistance of the load – typically 1 amp. A fuse is a conductor which will melt if the current exceed a certain limit. The 13 amp fuse in most plugs will blow and disconnect the circuit making it safe, If the current exceeds 13 (usually associated with a failure in insulation).

31. Fuse/MCB. Current limited by resistance of the earth wire – typically 50 amp - Fire Hazard.

32. Fuse/MCB. Circuit Isolated. Earthing provides a Safe Low impedence path for Fault Current.

33. Fuse/MCB. Leakage Current N.B. There are allways some small (and usually safe) currents flowing the casing to earth, and also from parts we connect to patients such as ECG Leads. These are called Leakage Currents and Manufacturers must design equipment To ensure all leakage currents are within safe limits.

34. Fuse/MCB.

37. The most common electrical fault in hospitals because cable are pulled by accident.

38. Fuse/MCB. N.B. If this happens you have lost the safety offered by the earth wire.

39. Fuse/MCB. You get the shock as the current has no safe path

40. What is an electric Shock ? First we will review nerve conduction. Then we will see that the normal action of nerve cells is interputed as current is passed through the body, Finally we will look at the different effects as the amount of current increases.

41. How Human Nerve Cells Transmit Signals. Dendrites Axon Synapse

42. How Human Nerve Cells Transmit Signals. Dendrites Axon Synapse K+K+ Na + The Axon maintains a chemical balance with more potassium ions inside the cell and sodiom ions outside the cell.

43. How Human Nerve Cells Transmit Signals. Dendrites Axon Synapse K+K+ Na + K+K+ When signal is transmitted the myelin sheet changes so that the sodium and potassium ions change places. This results in an electrical change in the cell and this in turn causes the next section of myelin to change.

44. How Human Nerve Cells Transmit Signals. Dendrites Axon Synapse K+K+

45. How Human Nerve Cells Transmit Signals. Dendrites Axon Synapse K+K+

46. How Human Nerve Cells Transmit Signals. Dendrites Axon Synapse K+K+

48. External Electrical Stimulation of Human Nerve Cells Electricity flowing through the human body can cause enough of a change in the electrical environment around a nerve cell to stimulate it.

49. Effects of Mains Derived Current on the Human Body. Macroshock: Direct Body Contact (only some of the current goes through the heart).

50. Effects of Mains Derived Current on the Human Body. Perception Can not let go Current Interuption of Normal Cardiac Function As current increases the effects get more severe. Tingly feeling Stimulates muscles And you cant let go

51. Effects of Mains Derived Current on the Human Body. Macroshock. Ventricular Fibrillation:I > 50 mA Can’t let go:I > 5 mA Tingling SensationI > 0.5 mA A mA is one thousenth of an Amp. So very small current can cause physiological effects. Leakage Currents can be dangerous.

52. Electrical Safety. 1.Properly fitted plugs 2.Plugs should have the correct fuse 3.Routine Safety Testing 4.Do not place fluids on top of electrical devices 5.Do not plug in equipment when you have wet hands 6.Report all faults 7.Report all frayed cables, broken plugs or any plugs that feel warm.

53. Now going to talk about Microshock. Read pages 265 to 268 in.. Science in Nursing and Health Care And an even better explanation on page 334 in…. Science in Nursing by Laurie Cree and Sandra Rischmiller 4 th Edition Published by Mosby. ISBN 0 7295 3260 7

54. Effects of Mains Derived Current on the Human Body. Microshock: Direct Cardiac Contact all current goes through the heart.

55. Microshock can occur in Hospitals. We often make a conductive connection with the heart - pacing wire - Central Line: saline fluid is conductive Even tiny current which we can not feel (below 0.5 mA) Are enough to cause heart failure (if greater that 0.05 mA).

56. C.D. Swerdlow, W.H. Olson, M.E. O’Connor, D.M. Gallik, R.A. Malkin & M.Laks. Cardiovascular collapse caused by Intracardiac Leakage Current. Circulation 1999 May 18; 99 (19): 2559 - 64 Intermittant VT0.02 mA Continuous VT0.03 mA Ventricular Fibrillation0.05 mA

57. Effects of Mains Derived Current on the Human Body. Macroshock. Ventricular Fibrillation:I > 50 mA Can’t let go:I > 5 mA Tingling SensationI > 0.5 mA Microshock. Ventricular Fibrillation:I > 0.05 mA

58. Effects of Mains Derived Current on the Human Body. Macroshock. Ventricular Fibrillation:I > 50 mA Can’t let go:I > 5 mA Tingling SensationI > 0.5 mA Microshock. Ventricular Fibrillation:I > 0.05 mA Safe Limits for allowable Currents that can flow from Devices. Body Contact. 0.1 mA Cardiac Contact. 0.01 mA

59. Effects of Mains Derived Current on the Human Body. Macroshock. Tingling SensationI > 0.5 mA Microshock. Ventricular Fibrillation:I > 0.05 mA Body Contact Staff or Patients. 0.1 mA Cardiac Contact. 0.01 mA

60. Patient Body Connection. For Electrical Parts that Come in Contact with the Body, the Leakage Current Must be below 0.1 mA. This symbol indicates that parts are safe to connect to a patients Body.

61. Patient Direct Cardiac Connection. For Electrical Parts that Come in Contact with the Heart, the Leakage Current Must be below 0.01 mA. This symbol indicates that parts are safe to connect to a patients Heart.

62. If you are handling patient connections that make direct cardiac contact you need to take particular care. Even if all devices are safe, the tiny currents of 0.01 mA can flow from the casing of of one device to another, through you or the patient and cause a Microshock to the Patient. The current is so small you wont feel it !

63. Micro Shock Risk – Reduced by use of Equipotential Bonding In areas where this happens (ICU’s CCU’s Cardiac Angio Labs etc) Extra bonding cables are used reduce the risk of Microshock. These are long green cables attached to the normal mains leads and they are plugged into special connectors.

64. Electrical Safety. 1.Properly fitted plugs 2.Plugs should have the correct fuse 3.Routine Safety Testing 4.Do not place fluids on top of electrical devices 5.Do not plug in equipment when you have wet hands 6.Report all faults 7.Report all frayed cables, broken plugs or any plugs that feel warm. 8.Use the extra bonding systems 9.Never touch pacing wire or CVP line and equipment at same time. Microshock Reduction.