Efficiency

1. Efficiency A lamp uses 100 Joules of electrical energy each second. Efficiency is the % transferred as useful energy Useful = the type the device was designed to produce

2. Efficiency formula - 1 Useful energy output Efficiency = X 100 for % Total energy input

3. Efficiency formula - 2 Energy wasted • Total energy input - Useful energy output =

4. Efficiency A lamp uses 100 Joules of electrical energy each second. It transfers this into • 80 Joules of heat • 20 Joules of light The lamp has an efficiency of 20% The Total wasted energy = 80 Joules

5. Useful energy? • Car – movement – wasted heat and sound • TV – light and sound – wasted heat • Body – movement and heat – some heat is wasted • Washing machine – movement and heat – wasted sound and some heat and shaking

6. Electricity Conservation Tips • Lighting Tips • Replace incandescent light bulbs with new, energy-efficient compact fluorescent lights. • Replace all bulbs with lowest acceptable wattages. • Use timers or motion detectors on lamps that are used for security lighting. • Use natural daylight as much as possible.

7. Cooling Tips • Keep your thermostat set at 25 degree; or higher, and on "auto," not "on." Each degree can mean up to 9% savings on cooling costs. • If your central or room air conditioner is more than 10 years old, it could be doubling your cooling costs. • Clean or replace your air conditioner filter monthly so your A/C runs efficiently. • Apply weather stripping and caulking around all doors and windows to keep the chilled air inside your house.

8. Electrical Hazards • Shock • Burns • Falls • Fire

9. Electrical HazardsElectrical Shock • Shock occurs when current passes through the body. • Severity of the shock depends on: – Path of current – Amount and type of current – Duration of exposure • Electrocution is a fatal electrical injury.

10. Electric Shock

11. Electrical HazardsConductors vs. Resistors continued… • Electricity wants to find the path of least resistance to the ground. • Human tissues and body fluids are relatively good conductors because of high water content. • So if a person touches an energized bare wire or faulty equipment while grounded, electricity will instantly pass through the body to the ground, causing a harmful, potentially fatal, shock.

12. Electrical HazardsGrounding • Grounding is a method of protecting employees from electric shock. • By grounding an electrical system, a low-resistance path to earth through a ground connection is intentionally created. • This path offers low resistance and has sufficient current-carrying capacity to prevent the build-up of hazardous voltages. • A three pronged cord offers a grounding connection.

13. Electrical HazardsGrounding continued… • Three wires for each cord and terminal. • A three prong plug has a hot prong, a return prong, and ground prong.

14. Electrical Hazards Ground Fault Accident Example A man was putting up lamp. When he went to plug in, his finger was touching the metal prong on the plug. His other hand was touching a metal coffee table leg for support. The current went through his body as a result, causing cardiac arrest and death.

16. Electrical HazardsElectrical Shock Example A worker came out of the bathroom with his hands dripping wet, and reached down to plug in a lamp. he got a shock but survived. The same worker was cleaning walls with a sponge and a bucket of soapy water. Not paying attention he washed over an outlet, which also gave his a shock. The shock was intensive enough to stop his breathing. he survived this time as well.

17. Electrical HazardsElectrical Burns • Most common nonfatal electrical injury. • Types: – Internal: “deep tissue”. – Skin: “entry” and “exit” points. – Arc: “flash” burns from heat and radiant energy. • Common sites of visible skin burns are the hands and feet.

18. How do birds sit safely on electric power lines? First, the facts: Electricity is always looking for the shortest and easiest path to the ground, a path that can include people and objects that touch or come too close to power lines. Electricity is fast—it travels at the speed of light in a vacuum—and it can cause severe burns or death if it flows through the human body.  Birds don’t represent a direct path to the ground, giving electricity nowhere to go but back to the wire. It’s easier for the current to simply stay in the wire. So touching a power line is not safe for humans. If the bird were to touch another line or pole the electricity would travel through the bird, either to the ground or another wire.

19. Why can a bird sit on the power line? • When does the current flow? • If there are voltage or potential difference, then the current starts to flow from high voltage to low voltage. But when a small bird sits on the power line, both feet are on the same voltage line! • Therefore, there are no potential difference between these two feet. Let's say the power line is very low, almost touching the ground, and a chicken is trying to cross it. If one leg is on the ground and the other one is on the power line, then there are potential difference between these two legs. Therefore, there is a flow of charge and eventually the chicken will be barbequed.

22. First Aid • Electric shock can cause: • respiratory paralysis. • heart fibrillation. • severe burns. • If the heart stops beating and breathing has ceased, the victim will suffer brain damage after four to six minutes. It is very important to respond quickly to an electric shock emergency. • The victim must first be separated from the source of the shock. • The best method is to cut off the power source. • Never touch a person until he or she has been separated from the power source, or you also risk being electrocuted. • Send for professional medical help immediately. • If the victim is not breathing, artificial respiration must be administered quickly. • When there is no pulse, coronary pulmonary resuscitation (CPR) should be started.

23. How to do CPR • If you are alone and are not trained in administering CPR, you should still attempt to revive the victim, because this may be the only chance for survival. • Tilt the injured person's head back. • pinch the nostrils closed with your fingers. • take a deep breath. • place your mouth over his or her mouth and blow. • Move your head away and allow the person to exhale. • Repeat. Position the heel of one hand on the lower half of the adult victim's sternum. • place your other hand on top of the first, and press down 1.5 to 2 inches. Fifteen compressions to two breaths should be repeated until professional help arrives.