8 some natural phenomenon

1. 1 won

people. It can sometime takes
a long time

2. a used ballpen refill and rub
rously with a piece of

polythene. Bring it close to small Collect the objects and the
pieces of paper. Take care not tc materials listed in Table 15.1. Try
touch the rubbed end of the

ith your hand or with a metallic

refill to charge each by rubbing with thi

materials mentioned in the Table
Record your finding

You can add more items
Table

ject. Repeat the activity with small
ry leaf, husk and mustard

pice th
eds, Record your observation:

Objects rubbed Materials ‘Attracts/does not | Charg
attract pieces | /not charged

used for rubbing

3. refill also with polythene. Bring it
close to the charged refill, Be careful
not to touch the charged end with
your hand, Is there any effect on
the refillin the tumbler? Do the
attract each other, or repel each
other

a) Inflate two balloons. Hang them Tita activi ye lave ent ee

in such a way that they do not touch :

together the charged objects that
each other (Fig. 15.1). Rub both the were inade of the same material

balloons with a woollen cloth and What happens iftwo charged objects
release them, What do you observe? made of different mate tale
brought close to each oth
find out
b) Rub a refill and place it gently in
glass tumbler as before (Fig. 15.3)
Bring an inflated charged balloon
near the refill and observe

let us repeat this y with
the used pen refills. Rub one refill
with polythene, Place it carefully in.
ass tumbler using the tumbler
as a stand (Fig. 15.2). Rub the other

Fig. 18.3 Une charg

4. with the end of the paper clip.
Observe what happens. Is there any
effect on the foil strips? Do they
repel each other or attract each
other? Touch now, other charged
bodies with the end of the paper clip
Do foil strips behave in the same
way in all cases? Can this apparatus
be used to detect whether a body i
charged or not? Can you explain
why the foil strips repel each other?

Iihemseives. When charges move, they
[constitute an electric current. You hav
about electric current Siné

The current in a circuit which

ul glow, or the current that

a wire hot, is nothing but al

Imotion of charges

ctivity 15.4

Take an empty jam bottle. Take a
piece of eardbe

ze than the mouth of the bottle
Pierce a hole in it so that a metal
paper clip could be inserted. Open
out paper clip as shown in F

Cut two strips of aluminium foil
about 4 em x 1 em each. Hang them
n the paper clip as shown. Insert
the paper clip in the cardboard lid
so that it is perpendicular to it (Fig
5.4). Charge a refill and touch it

9. hat could cau
disturbance inside
the earth?

Take an outline map of the world.
Locate the eastern coast and

Andaman and Nicobar Islands in
India. Mark other countries around
the Indian Ocean which could have
suffered damage. Collect account:
of the devastation caused by the
tsunami in India from your parents
or other elders in the family or in
the neighbourhood.

andmother told me
that the earth is balanced
on the horn of a bull and

when the bull shifts it
he other horn, an
earthquake takes place

How could it be true

NS

11. The tremor
waves. The
Fig. 15.19).

The pen records the
hs

vibrating

sip oat

ob 2

\

Like many other scale

produce waves

The instrument is
"hen tremors

n the surface of the earth. These are called seismic
are recorded by an instrum

‘nt called the seismograph
imply a vibrating rod, or a pendulum, w

tached to the vibrating sy
on a paper which moves under 4

construct a complete map of th
in Fig 15.14
its power

eismie wav By studying
can arthqui ho
They can also estimat

cause destruction,

Fig. 15.14 anhquake

not linear. Thi
half times the de

2 in magnitude me
an earthquake of
energy than an earthquake

nee (decibel is another e
means that an earthquake

xample), Richter scale Is
of magnitude 6 does not have one

of an earthquake of magnitude

means 1000 times more destructh
magnitude 6 has thous:
of magnitude 4.

and
à. In fact, a
energy. For
‘destructi

13. WHAT YOU HAVE LEARNT

EARTHQUAKE Like charges repel and unlike charges attract
macros The electrical charges produced by rubbing

When charges move, they constitute an

‘CONDUCTOR

ect current
An electro ay be used to detect

NEGATIVE CHARGE whether a body is changed orn

- of transfer of charge from a
POSITIVE CHARGE the earth i called earthing

teen different
SEISMOGRAPH.
= Lightning strik he and

THUNDERSTORM shining con buildings

trembling ofthe car
TSUNAMI Barthquake ia caused by a disturbance à

= itis not possible 1 predict the eccurrenc

ves from earthquakes.

15. |

u