NEBOSH CC Electrical Hazards on Site

Question 1

What voltage is used as the standard supply for portable power tools on UK construction sites to reduce electrocution risk?

Accepted Answer

110V centre-tapped to earth (CTE)

Answer

110V centre-tapped to earth (CTE) is used on UK construction sites. The transformer centre tap is earthed so the maximum voltage to earth is 55V, significantly reducing the severity of an electric shock compared to 230V.

Question 2

What colour is typically used for 110V electrical supply equipment on UK construction sites?

Accepted Answer

Yellow

Answer

110V electrical equipment and leads on UK construction sites are colour-coded yellow to distinguish them from 230V (blue for single phase) and 415V (red for three phase) equipment, helping workers identify the correct supply voltage.

Question 3

What is the primary hazard when using electrical equipment near water on a construction site?

Accepted Answer

Electrocution from current passing through the water

Answer

Water is a conductor of electricity. When electrical current passes through water, anyone in contact with the water who is also touching an earthed surface can receive a lethal electric shock.

Question 4

What device provides protection against electrocution by detecting earth leakage current and cutting off the supply within milliseconds?

Accepted Answer

Residual Current Device (RCD)

Answer

A Residual Current Device (RCD) detects any difference between the current in the live and neutral conductors, indicating a fault or leakage to earth, and disconnects the supply within 30 milliseconds — fast enough to prevent electrocution.

Question 5

What does 'dead working' mean in the context of electrical safety?

Accepted Answer

Working on electrical equipment that has been isolated and proved dead before work begins

Answer

Dead working means all electrical equipment and conductors in the work area are isolated from the electrical supply and proved dead (tested) before work begins. This is the safest method of working on electrical systems.

NEBOSH Construction Certificate Practice Test

NEBOSH Construction Certificate Practice Test

NEBOSH CC Electrical Hazards on Site