Domestic Wiring and Illumination Questions and Answers

Answer: B

The miniature components on a printed circuit board are damaged by too much heat, so the soldering method preferred is temperature controlled soldering, in which the iron tip is held at a set temperature. Flame soldering heats a large area and would damage the board, machine soldering such as wave soldering is used for large production runs, and hot gas soldering is used for surface mounted work with special equipment. The answer is temperature controlled soldering, option (B).

Answer: B

The key gives coarse solder as the one preferred for a job made of copper. Soft solders are alloys of tin and lead in different proportions, and a coarse solder, with more lead, melts over a wider range and is used for heavy joints and thicker copper work, while fine solder, with more tin, is used for electronics. Electrician's solder and electrician's fine solder are names of the types used for wiring and fine work. The answer is Coarse solder, option (B), and the item is a recall question.

Answer: D

Electrical energy is the power multiplied by the time. The kettle is rated at 750 W and used for 90 minutes, which is 1.5 hours, so the energy is power in kilowatts times time in hours.

\[ E = 0.75\ \mathrm{kW} \times 1.5\ \mathrm{h} \]

\[ E = 1.125\ \mathrm{kWH} \]

So the energy consumed is 1.125 kWH, option (D). The other values do not follow from 750 W and 1.5 hours; 2.22 kWH, 8.1 kWH and 13 kWH are too large for such a kettle.

Answer: C

When a rivet is placed near the edge of a metal plate, the metal between the rivet and the edge can tear out if the rivet is too near. To avoid tearing, the distance from the edge of the metal to the centre of the rivet is taken as 2D, where D is the diameter of the rivet, which is the key's answer, option (C). A distance of 1D would be too small and the metal would tear, while 3D and 4D waste material without any need.

Answer: B

The symbol shown, a dome-shaped outline fixed on a line, is the electrical symbol of a buzzer, a device that gives a continuous sound when it is supplied with a voltage. A bell is drawn as a similar dome with a clapper, a circuit breaker is drawn as a switch with a contact, and a panic lamp is drawn as a lamp symbol. The answer is buzzer, option (B), and the item depends on recognising the symbol.

Answer: B

The diagram gives dimensions of the run of the conduit or wiring along a wall and ceiling, with the distances 250, 150, 300, 600 and 450 and the positions of points and fittings drawn to scale. A drawing of this kind, which shows where the points and the runs are placed in the building, is a layout diagram, option (B). An installation plan shows the whole installation on the building plan, a circuit diagram shows the electrical connections in symbols, and a wiring diagram shows the connections of the individual wires. The key gives the layout diagram.

Answer: D

The Indian wiring rules limit the load on a power sub-circuit so that its wires and its protective device are not overloaded. The key gives the limit as 3000 W for each power sub-circuit, option (D). The lower values of 2000 W and 1500 W are more suitable for lighting sub-circuits, and 5000 W is above the limit the key gives for a sub-circuit. The question is a recall item of the regulations and the key is followed.

Answer: C

The tool has a hardened conical point at one end and a knurled grip, with a flat head at the other end that is struck with a hammer. It is a centre punch, which makes a small dent on metal to mark the centre of a hole and to guide the drill. A mallet has a large head, a chisel has a cutting edge, and a rawl plug jumper is a long tool with a flat or cutting bit used to make holes in walls. The answer is Centre punch, option (C).

Answer: B

In the middle half-lap joint the thickness of each piece is halved where they meet, so that one part sits in the notch of the other with the surfaces flush. It is used when one part of a job meets another part at some distance from the ends, as in the cross rail of a frame meeting an upright. The other options describe a cross half-lap or an end half-lap, in which the parts cross each other at or near the ends, or they say it can be used anywhere, which is not a case of use. The answer is option (B).

Answer: A

The Goliath Edison screw lamp holder is a large screw-type holder used for lamps of high wattage, where the heat of the lamp would damage an ordinary plastic. Its cover is therefore made of porcelain, which withstands high temperature and is a good insulator, and it is a material that does not burn. Bakelite, PVC and rubber soften or burn at the temperatures near a high-power lamp. The answer is porcelain, option (A).