· A bad egg floats in water because the up-thrust produced on account of
displaced water by the immersed portion of the bad egg is greater than the
weight of the egg.
· A copper vessel left in the air for a long time turns green. This is due
to the formation of copper carbonate when copper reacts with carbon dioxide and
moisture present in the air.
· A lightning conductor is fixed to tall buildings to protect them from
the destructive effects of the lightning.
· A man weigh more at the poles than at the equator because the polar
radius of the Earth is less than the equatorial radius .Hence the gravitational
pull is more at the poles than at the equator.
· A perspiring man feels relief when air floats by his side because the
flow of air increases the rate of evaporation of perspiration from the body.
· A sliced apple, when exposed to air, turns brown after some time as it
contains iron which gets oxidised and gives the fruit a brownish colour.
· A small space is left between each set of two rails of railway line to
allow for their expansion in summer.
· A swimmer just out of the river feels cold particularly if it is windy,
because of the evaporation of water from his body surface. The evaporation is
more on a windy day.
· A thick glass tumbler often cracks when very hot liquid is poured into
it because the inner surface of the thick glass tumbler coming in contact with
the hot liquid expands more in comparison with the outer surface which has
relatively lower temperature. This unequal expansion of inner and outer surface
causes the tumbler to crack.
· A train stops when the chain is pulled because of the following
mechanism. When the chain is pulled, one small valve gets opened and air enters
to the underside of the piston head of the brake cylinder through pipe
connection. Initially there is vacuum on both top and bottom side of the piston
head. When air enters the underside of the piston head, the piston raises up
due to difference of pressure and pulls the brake thus stopping the train.
· A wick in a stove keeps burning continuously as kerosene rises in the
wick due to capillary action.
· Alcohol is sometimes rubbed on the body of a person suffering from
fever. As soon as it is applied on the body, it evaporates taking away some
heat from the body. Since evaporation has a cooling effect, the body
temperature can be reduced by rubbing alcohol.
· An electric bulb makes a bang when it is broken because there is a
vacuum inside the electric bulb; when the bulb is broken air rushes in at great
speed from all sides to fill the vacuum. The rushing of air produces a noise
generally referred to as the “bang”.
· An ordinary clock loses time in summer because the length of its
pendulum increases, and therefore, its time period also increases. The pendulum
takes more time to complete each oscillation and thus loses time.
· Fish and
other aquatic creatures can live inside a deep frozen pond because there
will always be water just beneath the ice level .
· Food is cooked quickly in a pressure cooker because the boiling point of
water increases at high pressure. Food cooks faster at high temperature.
· Formation
of shadows can be explained by rectilinear propagation of light
· If a highly corked glass bottle full of water is left out of doors on a
frosty night and convert into ice. There is no room available for the increased
volume and this may result in bursting of the bottle.
· In a
freezer ice cubes will be formed more quickly in trays made of Aluminium
because it is a good conductor of heat.
· In mountainous regions, the atmospheric pressure is less than it is at
see level water, therefore, boils at a lower temperature(less than 100° C) and
food takes more time to cook.
· It is dangerous to sleep in an unventilated room with fire burning
inside because the fire produces carbon monoxide and carbon dioxide gases.
Carbon monoxide is poisonous and can cause death.
· It is more
difficult to walk on ice than on a concrete road because there is very
little friction between the ice and feet pressing it.
· Moisture gather on the outer surface of a glass tumbler containing cold
water because the water vapour present in the air get cooled and appear as
droplets of water on coming in contact with the cold surface of the glass
tumbler.
· Pieces of
camphor (कपूर) placed on water move about rapidly. This is
because of surface tension.
· Soft iron is used as an electromagnet because it remains a magnet only
while the current passes through the coil around it and loses its magnetism
when the current is switched off.
· Standing in double-decker buses, particularly on the upper floor, is not
allowed because on tilting, the centre of gravity of the bus gets changed and
it is likely to overturn.
· The basic
reason for the extraordinary sparkle of suitably cut diamond is that it has a
very high refractive index.
· The boiling point of seawater will be more than the boiling point of
pure water because the former contains salt and other impurities.
· The Earth rotates on its axis from west to east. This rotation makes the
sun and the stars appear to be moving across the sky from east to west.
· The filament of an electric bulb is made of tungsten because it has a
high melting point and can be heated to a high temperature to emit light.
· The freezing compartment inside a refrigerator is at the top because the
air in contact with it becomes cold and heavy and sinks downwards, cooling the
rest of the compartment.
