Questions #1 - 5 are based on the following passage and the chart below.

Electrical shock occurs when a person comes in contact with two conductors of a circuit or when the body becomes part of the electrical circuit. In either case, a severe shock can cause the heart and lungs to stop functioning. Also, severe burns may occur where current enters and exits the body.

When it comes to electric shock, it’s not the voltage but the current that kills. One hundred volts of alternating current (AC) can kill, but so can as little as 42 volts of direct current (DC). The real measure of a shock's intensity lies in the amount of current, measured in milliamperes (mA), that is forced through the body. Any electrical device used on a house wiring circuit—an electric drill, hairdryer, toaster or radio--can transmit a fatal amount of current, given the right circumstances. The chart below shows the effects of various currents.

At any point below 20 mA, breathing becomes laboured: breathing ceases entirely even at values below 75 mA. As the current approaches 100 mA an uncoordinated twitching of the walls of the heart’s ventricles (ventricular fibrillation) occurs. If breathing stops, artificial respiration is required to get the victim breathing again. If the heart is not beating, cardiopulmonary resuscitation (CPR) is necessary.

In any case, prevention is the best medicine for electrical shock. Electrician’s apprentices should have a working knowledge of the principles of electricity, respect all voltages, and follow all safety policies and procedures. Apprentices should also be encouraged to take a basic course in CPR (cardiopulmonary resuscitation) so they can aid a co-worker in emergency situations.

 

 

 

  Readings Effects
Safe Current Values 1 mA or less Causes no sensation - not felt.
1 mA to 8 mA Causes a sensation of shock, but is not painful. Muscular
control is not lost, so the person can let go at will.
Unsafe current values 8 mA to 15 mA Causes a painful shock. Muscular control is not lost and the person can let go at will.
15 mA to 20 mA Causes a painful shock. Control of adjacent muscles is lost; and the victim can not let go.
50 mA to 100 mA Ventricular fibrillation - a heart condition that can result in death - is possible at this level.
100 mA to 200 mA Ventricular fibrillation occurs.
200 mA and over Causes severe burns and severe muscular contractions. Contractions are so severe that chest muscles clamp the heart and stop it for the duration of the shock. (This prevents ventricular fibrillation).