Explain about electroscope with an activity
Answers
Answer:
ELECTROSCOPE : Electroscope is used to detect and measure electric charges.
WORKING OF AN ELECTROSCOPE
•In an uncharged electroscope, the leaves hang straight down.
•When a charged object touches the metal knob, electric charges travel down the rod and into the leaves.
•The leaves spread apart, indicating the presence of an electric charge.
•Since the charge on both leaves is the same the leaves repel each other and spread out.
CONSTRUCTION OF AN ELECTROSCOPE :
An electroscope consists of a metal rod with a knob at the top and a pair of thin metal leaves at the bottom. The rod is inserted in a one hole rubber stopper which fits into a flask.The flask contains the lower part of the rod and the metal leaves.
HOPE THIS WILL HELP YOU
Answer: Refer page no. 3-5 chapter-1 ncert class 12 part-1 physics.
Checkout the attachment file for ncert text book physics class-12.
Hope this will help you.
Explanation:
A simple apparatus to detect charge on a body is the gold-leaf
electroscope [Fig. 1.2(a)]. It consists of a vertical metal rod housed in a
box, with two thin gold leaves attached to its bottom end. When a charged
object touches the metal knob at the top of the rod, charge flows on to
the leaves and they diverge. The degree of divergance is an indicator of
the amount of charge.
4
Physic s
Students can make a simple electroscope as
follows [Fig. 1.2(b)]: Take a thin aluminium curtain
rod with ball ends fitted for hanging the curtain. Cut
out a piece of length about 20 cm with the ball at
one end and flatten the cut end. Take a large bottle
that can hold this rod and a cork which will fit in the
opening of the bottle. Make a hole in the cork
sufficient to hold the curtain rod snugly. Slide the
rod through the hole in the cork with the cut end on
the lower side and ball end projecting above the cork.
Fold a small, thin aluminium foil (about 6 cm in
length) in the middle and attach it to the flattened
end of the rod by cellulose tape. This forms the leaves
of your electroscope. Fit the cork in the bottle with
about 5 cm of the ball end projecting above the cork.
A paper scale may be put inside the bottle in advance
to measure the separation of leaves. The separation
is a rough measure of the amount of charge on the
electroscope.
To understand how the electroscope works, use
the white paper strips we used for seeing the
attraction of charged bodies. Fold the strips into half
so that you make a mark of fold. Open the strip and
iron it lightly with the mountain fold up, as shown
in Fig. 1.3. Hold the strip by pinching it at the fold.
You would notice that the two halves move apart.
This shows that the strip has acquired charge on ironing. When you fold
it into half, both the halves have the same charge. Hence they repel each
other. The same effect is seen in the leaf electroscope. On charging the
curtain rod by touching the ball end with an electrified body, charge is
transferred to the curtain rod and the attached aluminium foil. Both the
halves of the foil get similar charge and therefore repel each other. The
divergence in the leaves depends on the amount of charge on them. Let
us first try to understand why material bodies acquire charge.
You know that all matter is made up of atoms and/or molecules.
Although normally the materials are electrically neutral, they do contain
charges; but their charges are exactly balanced. Forces that hold the
molecules together, forces that hold atoms together in a solid, the adhesive
force of glue, forces associated with surface tension, all are basically
electrical in nature, arising from the forces between charged particles.
Thus the electric force is all pervasive and it encompasses almost each
and every field associated with our life. It is therefore essential that we
learn more about such a force.
To electrify a neutral body, we need to add or remove one kind of
charge. When we say that a body is charged, we always refer to this
excess charge or deficit of charge. In solids, some of the electrons, being
less tightly bound in the atom, are the charges which are transferred
from one body to the other. A body can thus be charged positively by
losing some of its electrons. Similarly, a body can be charged negatively
FIGURE 1.2 Electroscopes: (a) The gold leaf
electroscope, (b) Schematics of a simple
electroscope.
FIGURE 1.3 Paper strip
experiment.
Ele c tric Cha rg e s
a nd Fie ld s
5
by gaining electrons. When we rub a glass rod with silk, some of the
electrons from the rod are transferred to the silk cloth. Thus the rod gets
positively charged and the silk gets negatively charged. No new charge is
created in the process of rubbing. Also the number of electrons, that are
transferred, is a very small fraction of the total number of electrons in the
material body. Also only the less tightly bound electrons in a material
body can be transferred from it to another by rubbing. Therefore, when
a body is rubbed with another, the bodies get charged and that is why
we have to stick to certain pairs of materials to notice charging on rubbing
the bodies.