PHYSICS [2 Mark Question Answer]

Harmful effects of global warming are:
(a). The atmospheric temperature of the earth would increase thereby making it difficult for a living being to survive.
(b). It would melt down the polar caps thus increasing the size of the ocean and leading to floods, tsunami, etc.
(c). The increase in temperature would affect climate and rainfall thus affecting flora and fauna.
(d). Human beings would be vulnerable to diseases as microbes would get warmth to grow.

The greenhouse is a glasshouse constructed to keep delicate and rare plants that require warmth and protection from the weather. It is constructed by panels of glass. The temperature in a green house 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. This phenomenon is called the greenhouse effect.

Take two sheets of tin plates, one blackened and the other is polished brightly. Fix some drawing pins on the outer side of both sheets using wax. Fix these plates vertically at a very short distance apart. Place a Bunsen burner midway between them. When you light the burner you will observe that the pins from the black painted sheet start dropping while the pins on the polished surface remain in the same position for a much longer time.
Thus, we can conclude that the black surface is a better absorber of heat than the polished one.

The flask consists of a double-walled glass container with a vacuum between the walls A and B. The inner side of A and the outer side of B are silvered. It has a narrow mouth which is closed by a non-conducting rubber stopper.
If a hot liquid is placed inside the flask, it cannot lose heat by conduction or convection, as there is no air between the walls. The small amount of heat lost from the liquid by radiation is reflected back into the liquid by silvering of the inner wall A and any radiation striking the outer wall B, is reflected back and prevented from reaching the liquid.

Smoke is entering into the box from tube Pandas smoke reaches near the candle its temperature increase and smoke become lighter and leaves out from tube Q.

We know C/100 = (F - 32)/180.
C =5/9 (F- 32 )
9/SC + 32 = F
F = 9/ SC + 32.
The graph between T°F and T°C is a straight line having a slope of 9/5 and the intercept on Y-axis is 32.

We know C/100 = (F - 32)/180.
C =5/9(F - 32)
C = 5/9F - 17.77.
The graph between T°C and T°F is a straight line having a slope of 5/9 and the intercept on the Y-axis is-17.77.

Three advantages of using mercury as a thermometric liquid:
(i) Mercury is a good conductor of heat.
(ii) Mercury has a high coefficient of expansion thus is sensitive to the smallest change in temperature.
(iii) Freezing points is very low and the boiling point is high.

Three properties of a liquid which make it suitable to be used in a thermometer are:
(i) The substance should have a high coefficient of expansion so that it is sensitive to the smallest change in temperature
(ii) The substance should have uniform expansion all over its entire volume
(iii) The substance should have minimum specific heat so that it absorbs minimum heat from the body under measurement.

When boiling water is poured into a glass bottle, it generally cracks because on pouring hot water in the bottle 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 bottle cracks.

The level will rise above X when the flask is kept in a hot water bath because the water in the flask will heat up and expand in volume thus raising the level of water in the tube above X

The diagram is to show how the given strip bends and cools. Due to heating, the copper bends more than invar due to the high coefficient of linear expansion of copper.

Two different metals are used for regulating temperature in an electrical device as the strip bends due to different coefficients of expansion on excessive heating due to current, thus breaking the electrical circuit until the strip cools down to a preset point.

It can be seen from the graph that the volume of the water decrease from 0°C to 4°C and the volume is minimum at 4°C. After 4°C, the volume increases with the increase in temperature.

If the Coefficient of Linear expansion is denoted by α
Coefficient of superficial expansion is denoted by β
And Coefficient of volume expansion is denoted by γ
Then the relation between α, β and γ is stated as
β = 2 α and γ = 3 α
α : β : γ : : 1 : 2 : 3

On heating the copper washer
(a). Its internal diameter will increase as the copper washer expands outwards
(b). Volume will increase as the size of the metal expands on heating
(c). Mass will remain the same as the mass does not change with change in temperature
(d). Density will decrease as the volume of the washer increases on heating and density is inversely proportional to volume
(e). External diameter will increase because the copper washer expands outwards

A hot glass chimney often crack when a drop of water falls on it because the glass of the chimney expands due to constant heating by the flame of the chimney but as a cooler water drop falls on the glass, the outer surface contracts more than the inner side of the glass. This unequal contraction between the two surfaces causes a strain and the glass cracks.

No, both liquids i.e. mercury and alcohol will not have the same volume on heating as they have a different coefficients of expansions, thus they expand differently on heating at the same temperature range. Alcohol expands more than mercury.

When a liquid is heated in a flask. Due to heat, the flask expands along with the liquid, thus providing more space for the liquid. Hence the level of the liquid falls. Thus this dropped level shows the apparent expansion of the liquid. The actual expansion of the liquid, when heated, is the real expansion.

Harmful effects of global warming are
(a). The atmospheric temperature of the earth would increase thereby making it difficult for a living being to survive
(b). It would melt down the polar caps thus increasing the size of the ocean and leading to floods, tsunami, etc.
(c). The increase in temperature would affect climate and rainfall thus affecting flora and fauna.
(d). Human beings would be vulnerable to diseases as microbes would get warmth to grow.

Lower fixed point = 10°C
Upper fixed point =130°C
Range of thermometer= 130°C - 10°C
= 120°C
No of divisions = 100
So least count = 120/100 = 1.2°C
On actual thermometer 40°C would have 40 divisions
So, on this thermometer, it would show
= 40 x LC = 48°C

In the diagram, it is clear that the ice will melt faster in the flask than in the test tube because water is a bad conductor of heat and the transfer of heat in liquid through convection is from bottom to top.

It can be seen from the graph that the volume of the water decrease from 0°C to 4°C and the volume Is minimum at 4°C. After 4°C, the volume increases with the increase In temperature.

Variation of the volume of water with temperature

The level Y will rise and level X will drop because the air in blackened bulb is heated more than clear bulb; hence the air expands and pushes the mercury to the other limb.

The heat produced in various conversion processes like production, consumption, etc is not returned to the sun. Thus the energy flow of the sun-eco system is not cyclic.

The spiral starts moving because due to the flame of the candle the spiral heats up and expands. While expanding, the spiral tries to create space for the extension in length, and an outward pull is created which causes the spiral to move.

The cold air that blows from the land towards the sea during the night, is called a land breeze The cold air that blows from the sea towards the land during the day is known as the sea breeze. These breezes are examples of a natural convection current.
Natural convection currents

Water is a bad conductor of heat
An ice cube is wrapped into a wire mesh and is put at the bottom of the glass test tube. The test tube is then heated near the top of the water. It will be noticed that though the water at the top starts boiling, the ice at the bottom does not melt. This clearly shows that water is a poor conductor of heat. "

Three modes of heat transfer are
(a). Conduction involves the transfer of heat from the hot end to the cold end from particle to particle of the medium.
(b). Convection is the transfer of heat from one body to another by the actual movement of the particles of the medium
(c). Radiation is the transfer of heat from one body to another without the need of an intervening material medium

Diagram of six's maximum and minimum thermometer

Six's thermometer is a thermometer which can measure the maximum and minimum temperatures reached over a period of time, usually during a day. It is commonly used wherever a simple way is needed to measure the extremes of temperature at a locat ion, for instance in meteorology and horticulture

A clinical thermometer is used to measure body temperature. The capillary tube has a constriction above the bulb preventing mercury to fall back once it has risen

The main characteristics of the thermometric substances are
(a). The substance should have a high coefficient of expansion so that it is sensitive to the smallest change in temperature
(b). The substance should have uniform expansion all over its entire volume
(c). The substance should have minimum specific heat so that it absorbs minimum heat from the body under measurement.

No, it is not possible to heat a liquid or gas from above because the transfer of heat through convection takes place vertically upwards in liquids and gases. So if they are heated from above, the liquid or gas at the top will only be heated because most liquids and gases are themselves bad conductors of heat so they cannot conduct heat from the top layer to the bottom layer.

The beams of the bridges expand maximum during the summer days and contract maximum during the winter nights. If the beams are fixed at both ends on the pillars, they may develop crack due to expansion and contraction. To avoid this, beams are made to rest on rollers on the pillars to provide space for expansion.

The cold air that blows from the land towards the sea during night, is called a land breeze. The cold air that blows from the sea towards the land during the day is known as the sea breeze. These breezes are examples of a natural convection current.

Not all substances expand on heating. Some examples of substances which do not expand on heating are plastics, polythene and rubber.

There are three types of thermal expansions:
a. Linear expansion
b. Superficial expansion
c. Cubical expansion
Coefficient of linear expansion be a Coefficient of cubical expansion be γ The relation between them is V = 3 α