Electrical NEC QUESTIONS

Question 1 Where an installation and generator are not permanently fixed, protection against indirect contact must be provided by the use of a residual current device. The rated residual current (IAN) of such a device must not exceed 10mA 30mA 100mA 500mA Question 2 The minimum cross-sectional area of the protective conductor used within a final circuit, having high protective conductor currents in excess of 10 mA when supplying more than one item of electrical equipment, may be 4 mm2, provided that additional protection from the use of a residual current device is present the protective conductor has additional mechanical protection individual items of equipment are supplied through an isolating transformer the protective conductor is in the form of a complete ring. Question 3 In Zone 2 of a bathroom, wiring systems embedded in the walls at a depth not exceeding 50 mm shall be limited to those which supply fixed equipment in Zones 1 and 3 0,1 and 2 0,2 and 3 1,2 and 3. Question 4 When carrying out a detailed inspection, which one of the following must be verified? The presence of fire barriers and protection against thermal effects, The prospective short circuit current at the origin. The maximum permissable voltage drop, The actual voltage drop Question 5 Control equipment incorporating overcurrent protection must be installed with every electric motor having a rating exceeding 0.37 kW 0.5 kW 1.0 kW 2.0 kW Question 6 A 13A socket-outlet, connected directly to a TN-C-S system, supplies portable equipment for use outdoors. Supplementary protection to reduce direct contact risk should be provided by means of a general purpose fuse miniature circuit breaker residual current device class II equipment enclosure

Question 7 The MINIMUM size of trunking required to enclose ten 6 mm2 and twenty 10 mm2 single-core thermoplastic (p.v.c.) cables is 10 x 38 mm 100x25 mm 100x50 mm 100x100 mm Question 8 The part of a fuse which is designed to melt when the fuse operates is defined as the fuse wire element link carrier. Question 9 To reduce the risk of shock from the metalwork of Class I street located equipment, protection should be by non-conducting location EEBAD earth-free equipotential bonding electrical separation Question 10 The circuit of a safety service shall be coloured red independent of any other circuit housed in compartmentalised trunking un-protected Question 11 For household installations, the maximum floor area that may be served by a single 30 A ring final circuit using socket outlets to BS 1363 is 20m2 100m2 200m2 unlimited Question 12 Where a residual current device is used in an installation, the product of its rated residual operating current and the earth fault loop impedance should NOT be greater than 2V 10 V 40V 50V. Question 13 Which one of the following items must be included in a test sequence? Identification of conductors, Protection against indirect contact, Adequacy of access to switchgear. Operation of an r.c.d.

Question 14 A legible diagram, chart or table relating to an installation must be provided to indicate any circuit of equipment vulnerable to a typical test the location of all portable equipment for testing purposes that the original installation design has notchanged. Question 15 Other than within site offices, toilets etc., every plug and socket outlet for use on a construction site shall comply with BS EN 60309-2 BS EN 60947-2 BS EN 60947-3 BS EN 60269-1 Question 16 In agricultural and horticultural installations, electrical equipment installed for normal use shall have a minimum degree of protection to IP22 IP33 IP44 IP55. Question 17 If a socket outlet has to be installed in Zone B of a small swimming pool, it must conform to BS EN 60898 BS 1363 BS6991 BS EN 60309-2 Question 18 An insulation resistance test set used to carry out an insulation test on a 400 V circuit MUST be capable, when loaded with 1 mA, of supplying a test voltage of 400V 500V 1000V 3750V Question 19 In a touring caravan, a notice indicating the nominal voltage, frequency and rated current of the caravan installation must be fixed inside the fuse box on or near the inlet recess on or near the front window on the towbar. Question 20 Which one of the following is NOT recognised by BS 7671 as suitable for acting as an earth electrode? Non-corrosive metallic coverings of cables. Earth plates. Underground structural metalwork embedded in foundations, Gas and water supply pipes

ANSWERS Question 1 Where an installation and generator are not permanently fixed, protection against indirect contact must be provided by the use of a residual current device. The rated residual current (IAN) of such a device must not exceed Correct Answer: 30mA Question 2 The minimum cross-sectional area of the protective conductor used within a final circuit, having high protective conductor currents in excess of 10 mA when supplying more than one item of electrical equipment, may be 4 mm2, provided that Selected Answer: additional protection from the use of a residual current device is present Question 3 In Zone 2 of a bathroom, wiring systems embedded in the walls at a depth not exceeding 50 mm shall be limited to those which supply fixed equipment in Zones Correct Answer: 1,2 and 3. Question 4 When carrying out a detailed inspection, which one of the following must be verified? Correct Answer: The presence of fire barriers and protection against thermal effects, Question 5 Control equipment incorporating overcurrent protection must be installed with every electric motor having a rating exceeding Correct Answer: 0.37 kW Question 6 A 13A socket-outlet, connected directly to a TN-C-S system, supplies portable equipment for use outdoors. Supplementary protection to reduce direct contact risk should be provided by means of a Correct Answer: residual current device Question 7 The MINIMUM size of trunking required to enclose ten 6 mm2 and twenty 10 mm2 single-core thermoplastic (p.v.c.) cables is Correct Answer: 100x50 mm Question 8 The part of a fuse which is designed to melt when the fuse operates is defined as the fuse Correct Answer: element Question 9 To reduce the risk of shock from the metalwork of Class I street located equipment, protection should be by Correct Answer: EEBAD Question 10 The circuit of a safety service shall be Correct Answer: independent of any other circuit Question 11 For household installations, the maximum floor area that may be served by a single 30 A ring final circuit using socket outlets to BS 1363 is Correct Answer: unlimited

Question 12 Where a residual current device is used in an installation, the product of its rated residual operating current and the earth fault loop impedance should NOT be greater than Correct Answer: 50V. Question 13 Which one of the following items must be included in a test sequence? Correct Answer: Operation of an r.c.d. Question 14 A legible diagram, chart or table relating to an installation must be provided to indicate Correct Answer: any circuit of equipment vulnerable to a typical test Question 15 Other than within site offices, toilets etc., every plug and socket outlet for use on a construction site shall comply with Correct Answer: BS EN 60309-2 Question 16 In agricultural and horticultural installations, electrical equipment installed for normal use shall have a minimum degree of protection to Correct Answer: IP44 Question 17 If a socket outlet has to be installed in Zone B of a small swimming pool, it must conform to Correct Answer: BS EN 60309-2 Question 18 An insulation resistance test set used to carry out an insulation test on a 400 V circuit MUST be capable, when loaded with 1 mA, of supplying a test voltage of Correct Answer: 500V Question 19 In a touring caravan, a notice indicating the nominal voltage, frequency and rated current of the caravan installation must be fixed Correct Answer: on or near the inlet recess Question 20 Which one of the following is NOT recognised by BS 7671 as suitable for acting as an earth electrode? Correct Answer: Gas and water supply pipes