8.2 Hazards of electricity

Question 1

The dangers (risk of personal injury) associated with electricity can be remembered by

Answer 1

the acronym B-SAFEBurns Shock Arcing Fire Explosion

Question 2

A direct contact refers to

Answer 2

a person coming into contact with a conductor which is live in normal circumstances. Protection against direct contact has been renamed basic protection

Question 3

An indirect contact refers to

Answer 3

a person coming into contact with an exposed conductive part which is not normally live, but has accidentally become live due to insulation failure or some other cause. Protection against indirect contact is now known as fault protection

Question 4

With respect to UK mains voltage electricity, outline the factors that determine the severity of the effects of an electric shock. 6 marks

Answer 4

(a) Factors include:  the voltage, the nature of the current (whether alternating or direct)  the body resistance of the individual with reference to age, gender, the amount of moisture (perspiration) on the body and the type of footwear worn  the route taken by the current through the body,  the speed of action of any protective measures  the environmental conditions, such as the floor material and the presence of water. Note: knowledge of Ohm’s Law could have been used to relate the size of current to voltage and resistance.

Question 5

Fires may be started by electricity in a number of ways. The principal mechanisms are: 4

Answer 5

(a) overheating of cables and electrical equipment due to overloading of conductors (b) leakage currents due to poor or inadequate insulation (c) overheating of flammable materials placed too close to electrical equipment which is otherwise operating normally (d) ignition of flammable materials by arcing or sparking of electrical equipment, including the scattering of hot particles from electrical equipment.