Most modern cameras make it impossible to make a double exposure unintentionally. But sometimes double or multiple exposures provide unusual and interesting results.
A few cameras have a switch or lever to allow the shutter to be retensioned without advancing the film to the next frame. This makes accurate register of the subject components possible and gives the most successful multiple exposures. Read the rest of this entry »
Socket-outlets situated off the main route of the cable do not have to be connected to the actual ring cable. Instead they are usually supplied from spur cables branching off the ring. These spurs are wired in the same size cable as that used for the ring.
Fixed appliances which may be connected to a ring circuit include skirting heaters, wall heaters, small water heaters and any non-portable electrical appliances having individual loadings of not more than 3000 W(13 A approx.). Read the rest of this entry »
A radial power circuit is the name given to a circuit supplying a number of 13 A socket-outlets and fixed appliances using one cable which is not wired in the form of a ring but terminates at the last outlet.
The permitted number of socket-outlets (and fixed appliances) depends on the current rating of the circuit which can be either 20 A, wired in 2.5 mm2 cable, or 30 A wired in 4 mm2 cable. The number of socket-outlets and fixed appliances which can be served by a 20 A radial circuit depends also on the location of the circuit and whether the outlets are confined to one room. Read the rest of this entry »
Joint boxes are usually circular and for part of the circuit wiring. They are fix permanently to the house structure are used principally in lighting circuits. Join boxes are available in 4- 5- and 6-terminal versions.
A 3-terminal joint box of 30 A current rating is used for ring circuits to connect spur cables to the ring cable, as shown the illustration. Read the rest of this entry »
A fused clock connector is a small non- switched fused outlet designed expressly for supplying a mains electric clock.
The unit is in two sections: a fixed base which is connected to the fixed circuit wiring, and another section in.the form of a flat pin plug which plugs into sockets in the base. The plug section carries the flex of the clock and contains the fuse. The plug is secured in the base by a retaining screw. This prevents the plug being pulled out accidentally and stopping the clock. Read the rest of this entry »
Table lamps, floor standards, bedside lights and other portable lights can have dimmer control using any one of three methods. One method is a dimmer socket adaptor which plugs into the standard 13 A socket-outlet. This unit has two 2-pin sockets and is especially suitable for controlling two bedside lamps in a twin-bedded or a double-bedded room. The control knob on the adaptor dims both lamps at the same light intensity; they cannot be controlled independently.
Another method uses a line-cord dimmer which is wired into the flex of the lamp. The dimmer can be a standard wall type mounted on a plastic box and placed on the arm of the chair, table, desk, or any other chosen position. Alternatively, it can be a mini-dimmer switch resembling a torpedo table lamp switch. This type is especially suitable for the individual control of bedside lamps. Read the rest of this entry »
Most people have a healthy respect for electricity and understand that it can be dangerous — even lethal — if misused. Electricity at all voltages should be respected. Anyone who does not follow the basic rules of electricity is not only a danger to himself but to everyone around him. Electrical accidents are avoidable: most are due to plain carelessness and failing to follow the basic rules.
There are about sixteen million homes in Britain supplied with electricity and each one contains an average of about 25 electrical appliances. Given the sheer number of items, it is perhaps surprising that there are fewer than 80 fatalities from electrical accidents a year. Although this represents only a small percentage of the entire population and represents only one per cent of the 8,000 deaths each year that result from accidents in the home, the figure is still far too high. Read the rest of this entry »
Don’ts
The earth path of an appliance can be checked easily using a simple test meter. Remember, path of low resistance is required from all items within a appliance that are linked into the earth path via the yellow and green cable.
The earth path of an appliance from its exposed metal parts to the earth pin of the plug should be a maximum of 1 ohm (BS3456).
Checking the earth path of a socket requires an earth loop test meter which needs to be operated correctly. This is an expensive item and, moreover, problems may be encountered with distribution boards fitted with an RCD. It is, therefore, advisable to have these tests done by a qualified electrical contractor. Read the rest of this entry »
Problems with electrical appliances may not always result from a failure of the equipment itself. They can be caused by the failure of electrical supply to the appliance via the socket. A three-pin socket must have a live supply, a neutral return and a sound earth path. When a plug from an appliance is inserted, firm contact must be made at all three points. If the live or neutral pins of the plug or connection point within the socket fail to make adequate contact or are free to move, localized heating will occur within the socket. Typical signs of this problem are listed below.
There are various reasons for such problems. They may be caused by one or a combination of any of those listed here. Read the rest of this entry »
