PHYSICS [1 Mark Question Answer]

Camel and are two animals which are able to increase their body temperature in summers and decrease their body temperature in winters.

Mercury, alcohol is commonly used in thermometers.

Fahrenheit invented the Fahrenheit scale of temperature.

Celsius invented the Celsius scale of temperature.

Temperature is the degree of hotness or coldness of a body compared to other bodies around it. SI unit of temperature is Kelvin (K)

Kelvin temperature scale is used in the SI system.

Water is not used as a thermometric liquid because it has a low coefficient of expansion so it is less sensitive to temperature changes. Moreover, it is transparent thus making it difficult to read the thermometer, and water evaporates with time thus producing an error, and also the freezing and boiling points are also low.

Two disadvantages of using mercury as a thermometric liquid:
(i) It does not have uniform expansion.
(ii) Mercury is less sensitive than alcohol as its coefficient of expansion is less than alcohol.

In cold countries water pipes burst in winter because the water has maximum density at 4°C and, due to anomalous expansion of water, it expands when the water is cooled to a temperature below 4°C

Telephone wires sag in summer because due to heat of the sun, the wire expands and increases in length, thus they sag in summer.

Anomalous expansion of water slows down the complete freezing of water in the lake.

When heated, water expands normally but the behavior of water is unusual over a small range of temperatures between 0 and 4°C. This is known as the anomalous expansion of water.

Two applications of the thermostat are in electric iron and in refrigerators.

The thermostat is a device for regulating temperature in electric circuits and it is made up of bimetallic strip.

Two applications of the bimetallic strip are thermostat in electric iron and in balance wheels.

A bimetallic strip consists of two metal strips- one with high coefficient of expansion and the other with low coefficient of expansion.

At 4°C, water has the maximum density due to anomalous expansion.

The given statement states that the change in length of the metal will be 0.000016 m when its temperature changes by 1°C.

The increase in the length of a rod depends on the following factors
(a). the material of the rod
(b). The original length of the rod
(c). Rise in temperature

The joints in metal pipes loosen in summers because the joints get more space to expand due to the heat in summers as compared to the pipes, therefore, the joints become loose in summers.

Two substances that contract on heating are plastic and poly-ethene.

Two substances that expand on heating are water and iron.

We should heat the neck of the bottle because due to heating the neck will expand and loosen the stopper stuck in the neck. In this way, we can easily remove the stopper from the bottle.

No, we cannot fuse iron wire in glass rod because glass is bad conductor of heat and it does not allow heat to pass through it and iron wire would not be able to get sufficient heat to fuse.

We should heat the neck of the bottle because due to heating the neck will expand and loosen the stopper stuck in the neck. In this way, we can easily remove the stopper.

Coefficient of Linear expansion is equal to the change in length of a rod of length 1m when its temperature rises by 1°C.

Celsius was the scientist who discovered the first thermometer in 1710.

Heat flows from a body at a higher temperature to a body of lower temperature.

The temperature in a greenhouse rises because heat enters the house through the glass but cannot escape out, because the glass reflects the heat back to the inside of the house. This makes the glasshouse warmer than the outside environment.

Global warming occurs due to the presence of carbon dioxide, CFCs, methane in the atmosphere. Carbon dioxide acts as a transparent gas to incoming shortwave radiations which the earth re-radiates into space. It, therefore traps the outgoing radiations thus warming the lower atmosphere of the earth thereby causing global warming.

The greenhouse is referred to as a glasshouse. The heat enters the house but cannot escape out, because the glass reflects the heat back to the inside of the house. This makes the glasshouse warmer than the outside environment. This phenomenon is called the greenhouse effect.

Temperature in °C = 1°C
C/100 = (F-32)/180
F = 1 x 18/10 + 32
= 33.8°F

Relative humidity is defined as the amount of water vapour in the air compared to the amount needed for saturation.

We feel cold on touching ice because heat flows from our warm hands to cold ice. Due to this flow of heat from hand to ice, the temperature of our hand falls. This is why we feel cold.

Pyrex glass tumbler does not crack on adding hot water because Pyrex glass has a low coefficient of expansion. It does not expand less when hot water is added to the tumbler.

When hot water is poured into a thick glass tumbler, it generally cracks because on pouring hot water in the tumbler the inner surface heats up and expands more as compared to its outer surface. This unequal expansion between the two surfaces causes a strain and the tumbler cracks.

The sensitivity of a thermometer can be increased by using a substance having a high coefficient of expansion and uniform expansion so that it expands with the slightest change in temperature.

Water is not used as a thermometric liquid because It has a low coefficient of expansion so it is less sensitive to temperature changes. Moreover, It is transparent thus making it difficult to read the thermometer, and water evaporates with time thus producing an error, and also the freezing and boiling points are also low.

Biogas is produced by the action of bacteria on decaying organic matter. The primary source of biogas in villages is the dung of cow or buffalo. The biogas is mostly methane which can be used as a chief source of light and heat energy.

SI unit of latent heat is Joule per kg (J/kg). >

Temperature is the degree of hotness or coldness of a body compared to other bodies around it. SI unit of temperature is Kelvin (K).

Any energy transfer is not 100% because energy is lost to the surroundings in the form of heat, friction losses during the transfer of energy. Therefore complete energy is not transferred.

The transformation of Sun's energy in the sun-eco system through a food chain is called energy flow.

People wear light colured clothes in winter because these clothes reflect most of the sun's radiations and absorb only a little of them. Therefore, they keep themselves cool.

Old quilts are less warmer than new ones because the cotton in the old quilt gets compressed and very little air will remain trapped in it, hence heat insulation is quite poor