Electric Shock

Electrical Installations:   Electric Shock.

Learning outcome

The learner will:

    Know and understand the requirements of electrical shock.

Assessment criteria
The learner can:

  1. Explain what is electric shock
  2. Specify the causes electric shock
  3. Explain the implications of electric shock
  4. Specify the requirements for dealing with electric shock.

What is electric shock?

Electric Shock: is the physiological reaction or injury caused by electric current passing through the body (human or animal).
Typically the expression is used to describe an injurious exposure to electricity.
Exposure to electrical energy may result in no injury at all or may result in a devastating damage or death.

Causes of electric shock

Electric shock may arise either by direct contact with a live part or indirectly by contact with an exposed conductive part that has been become live as a result of a fault condition such as: -
  * Broken equipment case exposing internal bare live conductors.
  * Crack equipment case causing tracking from internal live parts to external surface.
  * Damage supply cord insulation, exposing bare live conductors.
  * Broken plugs exposing bare live conductors.
  * Poor installation practice exposing bare live conductors at terminations.

Capacitors used in fluorescent fittings and single-phase motors are also a potential source of electric shock.

Effects of electric shock

The magnitude (size) and duration of the shock current are the two most significant factors determining the severity of an electric shock.
The magnitude of the shock current depends on the contact voltage and impedance (electrical resistance) of the shock path.
There is two shock paths namely: -
  1. The hand to feet route. The shock path impedance is the body impedance plus any external impedance.
  2. The hand-to-hand shock path is more dangerous, that is when one hand is in contact with an exposed conductive part...