Building Services Engineering 5th Edition Handbook

320 Electrical installations
51. Which is a typical time interval for a residual current device to open a 60 A circuit-breaker
double-pole switch when a fault current occurs?
1. 6 min.
2. 1 min.
3. 1 s.
4. 20 ms.
5. Less than 0.001 s.
52. What does RCD stand for?
1. Residual circuit device.
2. Residual current device.
3. Resistance circuit design.
4. Radio carbon dating.
5. Ratio circuit device.
53. Which is the most common form of mortality from electric shock?
1. Burns.
2. Ventricular fibrillation.
3. Muscle spasm.
4. Pain.
5. Bleeding.
54. Which is not a normal application for use of MICC wiring?
1. Fire alarms systems.
2. Public buildings such as theatres.
3. Tunnels.
4. Temporary buildings.
5. Power stations and heavy industrial buildings.
55. Why are cables installed within fixed conduit?
1. Hides ugly cables.
2. Conduit is a permanent fixture of the building while cables require replacement when
aged.
3. Conduit becomes earth continuity conductor.
4. Reduce heat emission from cables.
5. Protects PCV cables from heat gain from environment.
56. Which is correct about electrical systems?
1. Watts = volts × amps.
2. Three-phase current = 3 × single-phase current.
3. Watts and volt-amperes are always the same value.
4. Current = voltage × resistance.
5. Current measured in mega-ohms.