Explore topic-wise InterviewSolutions in Current Affairs.

(i) cooking gas – D 

(ii) alcohol – E 

(iii) wood – B 

(iv) hydrogen – C 

(v) kerosene – A

Fuel B is the most ideal fuel because. 

(i) it leaves no residue on burning. 

(ii) it has high calorific value of 48 kJ/g. 

(iii) it does not burn explosively.

Calorific value of LPG is 50kJ/gm means that if 1 gram of LPG is burnt completely, then it will produce 50kJ of heat energy.

(ii) Process-B is a chemical change.

(iii) Both processes A and B are chemical change.

Harmful changes:

• Rusting of iron
• Decaying of fruits.

Rusting of iron is harmful in the sense that it destroys iron articles slowly. As iron is used in making bridges, ships, cars, etc., it may cause huge monetary loss. Similarly decaying of fruits causes health hazards.

Prevention: Rusting can be prevented by oiling, polishing and painting. Fruits can be preserved by keeping them at low temperature and by using some specific preservatives.

Water fills up the gap between cracks. In winter the water freezes and expand exerting such a high pressure so the rocks breaks.

It is due to accommodate free expansion and contraction of the girder with change in temperature, if fixed at both ends, the girder will bend during summer and crack during winter.

The correct answer is graph c.

Explanation: 

The capillary rise h is inversely proportional to the radius of the capillary r. It means when r→0, h→∞ and when r→∞, h→0. This condition is best represented by the graph (c).

(c) The surface tension may be zero.

(d) The contact angle may be 90°.

Explanation: 

The rise in a capillary tube is given as, h = 2S.cosθ/rρg The capillary tube has a certain inner radius r. So r, ρ and g are not zero. For h to be zero either surface tension S may be zero or the contact angle θ = 90° so that cosθ = 0. But we can not conclude that S must be zero or θ must be 90°. Hence the option (c) and (d) are true.

No. 

Because the rise of a liquid in a capillary tube depends on other factors also as we can see in the expression for height h, h = 2S*cosθ/(rρg) 

The rise h depends on S, θ, r and ρ. Since it is a capillary tube, r is small and it can not make h zero. Even the density of a liquid ρ will not be so high to make h zero. But the cosθ can be zero for θ =90°, thus making the rise h =0.   

So if a liquid neither rises nor depresses in a capillary we can not conclude that the surface tension of the liquid is zero. The angle of contact between the liquid and the wall of the tube may be about 90°.

(a) the material of the solid
(b) the material of the liquid

Explanation: 

The contact angle between a solid and a liquid depends on the materials of the solid and the liquid. The same solid has different angle of contact with different liquids. The same liquid has different angle of contact with different solids. Hence options (a) and (b) are true. The contact angle between a solid and a liquid does not depend on the shape or the mass of the solid. 

Due to the surface tension, the surface of the liquid acts as a stretched membrane. So even if some more water than the rim level of the glass is poured into it, the stretched water surface which holds the glass rim due to adhesion becomes convex upward and the contact angle between the water and the glass becomes more than 90° in this situation. 

The zero degrees angle of contact for water and the glass is for the situation when the water level is below the rim level of the glass. In some special situations, the angle of contact may change.  

(a) the material of the solid
(b) the material of the liquid

Explanation: 

The contact angle between a solid and a liquid depends on the materials of the solid and the liquid. The same solid has different angle of contact with different liquids. The same liquid has different angle of contact with different solids. Hence options (a) and (b) are true. The contact angle between a solid and a liquid does not depend on the shape or the mass of the solid. 

At sunrise, the sun looks almost reddish because only red colour ( λb < λr ), which is least scattered is received by our eye and appears to come from the sun. Hence, the appearance of sun at sunrise, near the horizon may look almost reddish. 

(i) During the morning, sun rays travel large distances in the earth's atmosphere, and in this process, the shorter wavelengths scatter away and only large wavelength (red light) reaches us.

(ii) At noon, the sun is overhead and light -rays travel comparatively smaller distance and only a little of blue / violet light scatter, so the sun appears white. 

(iii) No atmosphere in outer space for scattering, so the sky appears dark.

The reason is that for a given angle of incidence, the angle of reflection is the same for all the wavelengths of white light while the angle of refraction is different for different wavelengths.

The phenomenon of scattering of light by the colloidal particles is called Tyndall effect.

Tyndall effect : When a beam of light is passed through a colloidal solution, placed in a dark room, the path of the beam becomes illuminated when observed through a microscope placed perpendicular to the path of light. This effect is called the Tyndall effect. 

Cause of Tyndall effect: The size of the colloidal particle is relatively larger than the solute particle of a true solution. The colloidal particles first absorb energy from the incident light and then scatter a part of this energy from their surfaces. Thus, Tyndall effect is due to scattering of light by the colloidal particles and the colloidal particles are seen to be moving as points of light moving against a dark background. 

Some daily phenomena based on Tyndall effect are as follows : 

(i) When a fine beam of sunlight enters a smoke-filled room through a small hole, the smoke particles become visible due to the scattering of light.  

(ii) When sunlight passes through a canopy of a dense forest, the tiny water droplets in the mist scatter light and become visible.

During pregnancy, the uterus expands, it’s normal size up to 500 times.

(a) The first period or menstruation is a point in time, known as Menarche. It usually begins between 12 to 15 years of age.

(b) 1. The sanitary pad and tampons should be wrapped properly and discarded because they can spread infections.

2. Sanitary pad or tampon should not be flushed down the toilet. 

3. Napkin incinerators are to be used properly for disposal of used Napkins.

c) No, it was not correct. The parents and teachers have to create awareness among the school girls about the use of Napkins and their proper disposal. Girls should be educated and should know the importance of such advertisement on Television.

Menstruation occur when the egg is not fertilized. Every month uterus prepares itself to receive the fertilized egg to nourish the embryo, its lining becomes thick and spongy for implantation of the fertilized egg.

In case egg is not fertilized thin lining breaks and discharged out of the body through the vagina in the form of blood.

This condition will not happen before puberty and during pregnancy

(d) Large feathery stigma

The membrane forming the surface layer of the ovum is called vitelline membrane.

(d) Fertilization

Menstruation is a periodical phenomenon that continues from puberty to menopause. This will happen if the released ovum is not fertilized by the sperm.

Gestation is the time period during which the embryo attains its development in the uterus.

A cord containing blood vessels that connects the placenta with the foetus is called the umblical cord.

Contraception is used to prevent pregnancy, to check population growth.

Reproduction is the process of producing offspring of their own kind.

Asexual and Sexual reproduction.

The fusion involving two polar nuclei and a sperm nucleus, that occurs in double fertilization in a seed plant and results in the formation of endosperm, is called the triple fusion

Dentine is the living tissue which forms the tooth.

walking-present participle acting as an adjective

Saliva is produced in the Salivary glands.

Cementum is a calcium-containing connective tissue that holds the tooth in the socket of the gum.

Blood carrying hormones to their target tissues.

• Eat plenty of fruits & vegetables every day 
• Eat less unhealthy food 
• Balance your food choices over time. (Draw a suitable picture using these ideas).

Mouth → buccal cavity → pharynx → Oesophagus → food into the stomach.

From

Mr.Sanjay,

7, Shanaz street,

TNGO Colony,

Adambakkam,

Chennai – 600088

30th September, 2020

To

The Editor

The Times of India

Chennai – 600001

Sir,

Sub: Importance of Conserving and Preserving Solar Energy Through the esteem column of your daily, I wish to bring to the Readers the importance to conserve and preserve solar energy.

Our colony Samba colony at Adambakkam uses Solar energy to lighten up the common area. Though we may save on electricity charges, it is important that we reduce the usage of solar energy also when not needed. I had noticed that in many areas the lights are not switched off in the mornings.

Although it may not be obvious, there’s a direct connection between your energy use and the environment. When you consume less power, you reduce the amount of toxic fumes released by power plants, conserve the earth’s natural resources and protect ecosystems from destruction. By taking steps to reduce your energy intake, you’ll contribute to a healthier and happier world. When you opt to cut back on energy use, you also help conserve limited natural resources that would otherwise be used to power the power plants. Less demand for energy creates less demand for harvesting fossil fuels.

Turning off the lights at night or washing clothes in cold water can save trees, coal, natural gas and more. From an economic standpoint, it’s critical to conserve our finite resources. Reducing electricity use in your home – or going off the power grid with solar energy -can benefit the environment, conserve resources and save lives. Although your own energy saving adjustments may seem inconsequential, small steps become great leaps when multiplied by the number of people living in the vicinity. Thereby I appeal to all the importance to conserve and preserve energy resources and save Mother Earth and lead a pollution free atmosphere.

Thank you

Yours faithfully

Sanjay

To

The Editor

The Times of India

Chennai – 600001

M. Hamel had been in the village for forty years.

(d) All the above

The process by which molecules are absorbed with the help of carrier Proteins against the concentration gradient is called active transport.

(a) Co – operative banks

Diffusion & Osmosis

The Raja Chelliah Committee on Trade Policy Reforms suggested the peak rate on import duties at 50%.