Page 126 - Science Class 07

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Electric Current and Circuit
• How does Electric Current Flow?
• Parts of Electric Circuit and its Symbols
• Effects of Electric Current
Electricity is one of the most important
blessings that science has given to mankind. It
has also become a part of modern life and one
cannot think of a world without it. Electricity
has many uses in our day-to-day life. It is used
for ligh ng rooms, working fans and domes c
appliances like using electric stoves, AC and
more. All these provide comfort to people. In
factories, large machines are worked with the
help of electricity. Essen al items like food,
cloth, paper and many other things are the
products of electricity.
Modern means of transporta on and
communica on have been revolu onised by it.
Electric trains and ba ery cars are quick means
of travel. Electricity also provides means of
amusement, radio, television and cinema,
which are the most popular forms of
entertainment. Modern equipment like
computers and robots have also been
developed because of electricity. Electricity
plays a pivotal role in the fields of medicines
and surgery too — such as X-ray, ECG. The use
of electricity is increasing day-by-day.
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• Electric Circuit
• Important Devices and Their Func ons
• Electric Bell
But do we know how electricity works for us?
The electricity that makes all these machines
work flows by means of wires in the form of
current. So, it is called current electricity.
Electricity is present even where there is no
electric wires. When you put off your shirt
made of synthe c cloth, you hear a crackling
sound. It is the sound that electric sparks
produce due to rubbing of the body with
synthe c cloth. As this electricity does not flow,
it is sta c electricity.
Greek ladies, in the past, wore yellow beads
round their necks. The beads got rubbed with
their smooth dresses and could pick up
feathers and bits of fluff. Greeks knew about a
solid called amber that could a ract feathers.
So, it was said that beads worn by women had
amber power. This name was given by William
Glibert, the doctor under Queen Elizabeth of
England. As the Greek word for amber is
electrum, the materials a rac ng feathers,
came to be called electric. It was in 1646, that
Dr Thomas Brown coined the word electricity.
Science-7