Page 51 - Innovator's Science-8

heat energy, making the wire warm. Different materials have different
amounts of resistance. For example, nichrome wire has more resistance
Science than copper wire of the same size and length, so it becomes hotter when
Bytes

Testimony current passes through it. This process, where a conductor gets heated by
the flow of electric current, is known as the heating effect of electric
Electric Bulb and
Fluorescent Lamp current.
An electric bulb produces Earlier, we have learnt that an incandescent lamp glows because its
light because a thin wire
inside it, called the filament is heated by an electric current. Many household appliances such
filament, becomes white- as electric heaters, stoves, irons, immersion rods, water heaters, kettles,
hot when an electric
current passes through it. and hair dryers work on the same principle of the heating effect of electric
The filament is usually current. All these devices contain a rod or a coil of wire, called a heating
made of tungsten, a element. In some appliances where this element is visible, it can be seen
metal that can withstand
very high temperatures. glowing red hot.
However, a large part of
the electrical energy in a
bulb is wasted as heat. A
fluorescent lamp works
differently. It contains
mercury vapour and a
fluorescent coa ng on its
inner surface. When a. b. c. d. e. f.
electric current passes Simple household electric heating appliances (a) Room heater; (a) R (b) Electric stove;
through the gas, it gives (c) Electric kettle; (d) Electric iron; (e) Water heating immersion coil; or (f) Hair dryer
off ultraviolet rays, which
make the coa ng glow The heating effect of electric current is very useful in many everyday
and produce visible light. appliances, such as electric heaters, toasters, and irons, where the heat is
Fluorescent lamps, and
modern LED lamps, use needed for work. However, it can also cause problems. When current flows
much less electricity than through long wires, some energy is lost as heat, which reduces efficiency. In
ordinary bulbs and are appliances, excessive heat can damage plugs and sockets by melting their
therefore more energy-
efficient and longer- plastic parts, and in extreme cases, it may even start fires. To prevent such
las ng. dangers in homes, safety devices like fuses and circuit breakers are included

in electrical circuits to stop excessive current flow and minimise overheating.

HOW DOES A BATTERY GENERATE ELECTRICITY?

Let us start with one of the earliest types of electric cells ever made.

Voltaic cell
A battery generates electricity through a chemical reaction between two

different metals separated by a chemical substance called an electrolyte .
A voltaic cell, also called a galvanic cell , is a device that produces electricity
from a chemical reaction. It has two metal plates made of different

materials, which are partly dipped in a liquid called an electrolyte. This

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