1. Instructor: Sujood Alazzam
PHYS 101
General Physics
Newton’s laws of Motion
Work, Energy and Power
Fluids
Direct Current (DC)
Nerve Conduction
Ionizing Radiation
Wave properties of light
Instructor: Sujood Alazzam
2017/2018

2. CHAPTER OUTLINE Chapter 17
Direct Current (DC):
17.1 Electric current.
17.2 Resistance
17.8 Electrical safety.

3. Lecture 12: Electrical safety

4. OBJECTIVES Describe how an electric shock affects the human body.
Discuss ways to avoid electric shock.

5. 17.8 Electrical Safety
A common phrase heard in reference to electrical safety is, “it is not the voltage that kills, it is the current”.

6. Electrical Safety
The wires which carry electricity consist of two parts:
The metal wires.
The plastic coating round the metal wires.

7. Electrical Safety The metal wires act as a conductor of electricity.
Conductors are materials which allow electricity to pass through them easily.
The plastic coating acts as an insulator which prevents people from being electrocuted.
Insulators are materials which do not allow electricity to pass through them easily.

8. The Plug

9. The Plug Most electric cables normally contain three wires:
The earth wire
The live wire
The neutral wire.

10. The Plug
You have to remember the names and colours of each of these three wires. You also have to remember the position of each of these three wires in a standard plug.
Here is the description of the graph. This chart is compatible with PowerPoint 97 – 2010.
Here is some more text. You may delete the graphical elements.
Wire
Insulation Colour
Location
Live
Brown
BR – bottom right
Neutral
Blue
BL – bottom left
Earth
Green/Yellow
Centre

12. ELECTRICAL HAZARDS Electric shock
Electrical shock occurs when the body becomes part of the electric circuit (the path through which current flows.

13. Electrical Safety Electricity is dangerous and can kill!!
An electric shock can:
Affect your muscles.
Affect your nerves.
Paralyse you.
Stop your heart beating.
You can get an electric shock from anything which is plugged in or connected to the mains supply.

14. ELECTRICAL HAZARDS Direct: Indirect:
Electrocution or death due to electrical shock
Electrical shock
Burns
Indirect:
Falls
Fire

15. Protective Devices
Fuses
The earth wire
The switch

16. Current is a flow of electricity and is measured in amps (A).
The Fuse
A fuse is a thin piece of wire which will melt when too much current passes through it.
Current is a flow of electricity and is measured in amps (A).

17. The Fuse
When the wire melts, all current is stopped from reaching the appliance and switches it off.
The fuse stops a large current from flowing through the appliance which could cause wires to overheat, melt or catch fire.

18. The Switch
Together, the fuse and switch control the amount of electricity that enters an appliance.
The fuse and the switch are connected to the live wire.
Electricity comes in through the live wire.
If the fuse is blown, or the switch is off, then the electricity cannot reach the appliance.

19. The earth wire does nothing unless something goes wrong.
The live and neutral pins allow electricity to pass through the appliance and cause it to work.
Plugs have 3 pins on them

20. Electrical Safety
It is very important that all plugs are wired correctly.
If they are not, then a number of things can go wrong!!!

21. 2. This makes the casing LIVE!
What can go wrong!
1. The most dangerous thing that can happen is that the live wire can become loose inside an appliance and touches the casing.
2. This makes the casing LIVE!
3. If you touch the LIVE casing, you could be electrocuted as you are providing a path for the electricity to flow.

22. Prevention
To prevent electrocution, the earth wire is connected to the casing of the appliance.
If the live wire touches the casing, the earth wire provides a path for the electricity to flow.
This blows the fuse and switches the appliance off, leaving you safe.

23. Effects of AC Electricity
Lung paralysis, usually temporary
Ventricular fibrillation, usually fatal
Muscle contraction “No Let Go” danger
Painful shock- cause indirect accident
More than 3 mA
More than 10 mA
More than 30 mA
More than 50 mA
Over 4 A Heart paralysis, severe burns

24. EFFECTS ON THE HUMAN BODY
Depends on:
Current and Voltage
Resistance
Path through body
Duration of shock

25. For more information you can see this website: https://www. youtube

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