Course AEEE 103 AUTO 108:

1
Course AEEE 103 / AUTO 108

• Text books
• Electrical Engineering Principles and
  Applications,
• 4rd Edition, by Allan R. Hambley, Prentice
  hall, 2008
• Hughes E, Smith I M, Hiley J, Brown K,
  Electrical and
• Electronic Technology, 10th Edition,
  Prentice Hall, 2008
• Prerequisites none
• Goals
• To introduce Mechanical Engineering students in
  the principles of Electrical Engineering. By the
  end of the course, students will become familiar
  with basic principles of electrical circuits,
  analogue and digital electronics.

2
Electric shock definition by Wikipedia

• An electric shock can occur upon contact of a
  human's body with any source of voltage high
  enough to cause sufficient current through the
  muscles or hair. The minimum current a human can
  feel is thought to be about 1 milliampere (mA).
  The current may cause tissue damage or
  fibrillation if it is sufficiently high. Death
  caused by an electric shock is referred to as
  electrocution.

3
Body Resistance

• The voltage necessary for electrocution depends
  on the current through the body and the duration
  of the current. Using Ohm's law, Voltage
  Current Resistance, we see that the current
  drawn depends on the resistance of the body. The
  resistance of our skin varies from person to
  person and fluctuates between different times of
  day. In general, dry skin is a poor conductor
  that may have a resistance of around 100,000 O,
  while broken or wet skin may have a resistance of
  around 1,000 O.

4
Electric shock
Fibrillation is the rapid, irregular, and
unsynchronized contraction of the muscle fibers
of the heart.
5
Example of Electric Shock

• Measurement of body resistance, gives a
  resistance of 500K Ohms. Using 9V and 500K Ohms
  in the equation, we come up with a current of 18
  microAmps, below the "feel" threshold of 1mA.
  However, removing the insulation of skin from our
  curious sailor here, the resistance through the
  very good conducting electrolytes of the body is
  sharply lower. Around 100 ohms, in fact,
  resulting in a current of 90mA - sufficient to
  stop our sailor's heart and kill him.

6
Electric Shock Factors

• The following factors determine the severity of
  the effect electric shock has on your body
• The amount of current that is flowing through
  your  body.
• The path the current takes through your body.
• The amount of body resistance you have to the
  current flow.
• The  length  of  time  the  current  flows
   through your  body.

7
Time of Current Flow

• The longer youre being shocked, the more chance
  there is for your heart to begin fibrillation.
  Fibrillation is the shocking of your heart into a
  useless flutter. Most people who die from
  electric shock die from fibrillation.
  Fibrillation in a normal adult is unlikely if the
  current in milliamperes  is  less  than  116/t,
   where  t  is  the  shock duration  in  seconds.
   The  longer  you  are  shocked,  the less
  current is needed to cause heart fibrillation.
  Here are   some   examples   of   shock   current
    levels   and durations that would cause
  fibrillation
• 21  milliamperes  for  30  seconds
• 44  milliamperes  for  7  seconds