MOCK EXAM from past papers - No. 1

31. Rating factors are applied to the fuse rating of a circuit to determine the minimum current carrying capacity of cables. A rating factor of 1 is used when a circuit is wired in 70 C thermoplastic insulated cable and operating in an ambient temperature of
a. 20 C
b. 25 C
c. 30 C
d. 35 C

32. Which one of the following is excluded from use as an earth electrode?
a. Earth plates
b. Welded reinforcement of concrete embedded in earth
c. Earth tapes
d. Gas and water utility pipes

33. A BS 3036 fuse, rated at 45A, is carrying a fault current of 145A, the protective device should operate in
a. 0.2s
b. 0.4s
c. 1s
d. 5s

34. The maximum earth fault loop impedance on a TN system for a ring final circuit protected by a 32A Type B MCB is
a. 1.37Ω
b. 1.09Ω
c. 1.84Ω
d. 2.64Ω

35. A permanent label should be fixed in a visible position at the point of connection of every earthing conductor to an earth electrode, with the wording
a. Danger Electrical Connection – Do not remove
b. Safety Electrical Connection – Do Not Remove
c. Danger Earth Connection – Do Not Remove
d. Safety Earth Connection – Do Not Remove

36. Which one of the following sources does not comply with BS 7671 as a SELV system?
a. A safety isolating transformer to BS EN 61558
b. A motor generator with windings providing equivalent isolation to that of a safety isolating transformer
c. A single-phase 55V to earthed midpoint transformer (414.3 (i) (ii) (iii) p58)
d. A 48V storage battery system

37. The minimum size of a copper earthing conductor buried in the ground that is not mechanically protected and not protected against corrosion is
a. 10 mm2
b. 16 mm2
c. 25 mm2
d. 50 mm2

38. When calculating the minimum value of the cross-sectional area of a protective conductor the following information is available Fault current = 650A Operating time of protective device = 0.3s Constant k, for protective conductor material = 115 The minimum cross-sectional area of the protective conductor must be
a. 2.5mm2
b. 1.5mm2
c. 6.0mm2
d. 4.0mm2

39. When a residual current device protects a socket-outlet in a domestic garage it must operate when
a. an earth fault on the garage lighting occurs
b. the protective conductor in a flexible cord to a lawn mower breaks
c. someone comes in direct contact with an exposed line conductor and earth
d. someone comes in contact with exposed earthed metalwork

40. Where an autotransformer is connected to a circuit having a neutral conductor, the common terminal of the winding shall be connected to the
a. neutral conductor
b. line conductor
c. protective conductor
d. bonding conductor

41. Circuit cables required to carry the starting, accelerating and load currents of motors should have a current rating not less than
a. full-load
b. 1.5 x full-load
c. 6 x full-load
d. 10 x full-load

42. As part of a detailed inspection which of the following must be checked?
a. The presence of fire barriers and protection against thermal effects
b. The prospective short-circuit current at the origin of the installation
c. The maximum permissible volt drop
d. The name of the manufacturer of any RCD fitted

43. Which of the following items should be included for checking during the initial verification of an installation?
a. Site works orders and alterations
b. Presence of diagrams and instructions
c. Minutes of all site meetings
d. All variations of contract

44. One item that should be included on charts and diagrams made available to the person carrying out the inspection and test is
a. all isolation and switching arrangements
b. the location details of portable equipment
c. the total number of outlets in the installation
d. the details of the original contract arrangements

45. The minimum value of insulation resistance when testing a 400V industrial installation is a. 0.25MΩ
b. 0.5MΩ
c. 1.0MΩ
d. 5MΩ