Electric - Its chemical effect | Electric - Its Heating Effect
Inside the glass bulb, a tiny conducting coiled coil of tungsten wire having high resistance is fitted and is called filament of the bulb The filament rests on two tiny wires called supporters and its ends are connected to leads through which electric current passes. The leads and filament supporters are fixed to a glass support, as shown in Fig. 8.18 and the upper portion is sealed with glass. Above the seal, an aluminium cap is attached and the leads are connected to the top of the cap as two terminals. On the lateral sides of the aluminium cap, two small projections are provided diametrically opposite to each other to help in fixing the bulb to its holder. As the resistance of the filament is much higher, it gets red hot and then emits. light when electricity is passed through it.
2. An Electric Stove: An electric stove consists of a porcelain base fixed in a casing and a filament fixed in the groove of the base. The filament is a long thin coiled wire and has high resistance. The ends of the thin filament is connected to the terminals by means of leads. When electric current passes through the filament, it gets red hot and generates heat, which can be used for cooking.
3. An Electric Iron: An electric iron contains a heating element, usually made of nichrome (an alloy of nic kel and chromium) placed between two mica sheets. These sheets are placed on an iron base, Above the mica sheets in which heating element IS placed, an asbestos sheet is placed and above that a dome is placed and fixed to the iron base. The ends of the heating element are connected to the mains through connecting wires. The mica sheets placed on either side of the heating element do not conduct electricity but transfer the heat. Thus, the iron base is heated and transfers the heat to the clothes being pressed. The asbestos sheet, placed above the mica sheet being a bad conductor of heat, does not allow the heat to move in the upward direction. A handle preferably made of ebonite is attached to the dome.
4. A Soldering Gun or Soldering Iron : We need to connect so many wires at so many places in a complex electric circuit . The connections are perfect when the joints of the wires are perfect . To have a perfect joint , the ends of the wires have to be joined in a molten state or a fused state . When the wires are made of less fusible material , in order to make the joint a perfect one , we use another fusible material , which is an alloy , to join the edges of the less fusible materials . This fusible alloy is called solder and the process of joining the wires with a solder is called soldering . For this purpose a metallic rod is used ; which is called soldering gun or soldering iron . One end of the rod is pointed and wedge - shaped and the other end is fixed to a hollow metallic tube . A heating element is placed inside the hollow tube and is in contact with the rod , as shown in the figure . To the other end of the rod , a handle preferably made of bakelite material is attached . The heating element in the soldering iron is connected to the mains by means of a connecting wire through the handle
5. Electric Immersion Heater : The heating element in an electrical immersion heater is usually made of nichrome ( an alloy of nickel and chromium ) wire wound in the form of a spring . The heating element is placed in a hollow brass tube . The space between the brass tube and the heating element is filled with magnesium oxide or quartz sand . This avoids the contact of the heating clement to the brass tube and avoids electric shock to the person handling it . The magnesium oxide or the quartz sand used in the heater is an electric insulator but is a good conductor of heat The ends of the beating element are connected to brass terminals fixed in a casing made of bakelite and the terminals are connected to the mains through a plus and wire . Nichrome has high electrical resistance and so it is the most preferred material for the preparation of heating elements. Electric Fuse : Electric frase is the device used in the household electric wiring that protects appliances from high current . Fixed wire is connected between the mains and leads of the primary circuit of an electric appliance . When excess amount of electricity passes through the wire , the fuse wire gets heated and the heat produced fuses or melts the wire breaking the power supply to the circuit of the appliance . Thus , the electric appliance is protected from the passage of high electric current which destroy the appliance.