Explore topic-wise InterviewSolutions in Current Affairs.

(क) मुख्यतः जीवाश्म ईंधन पेट्रोलियम और कोयला है।
(ख) सभी प्राणी अपना भोजन सूर्य से प्राप्त करते हैं।
(ग) बायोगैस मुख्यतः मेथेन और कार्बन डाइऑक्साइड का मिश्रण है।
(घ) जलविद्युत संयंत्र का मुख्य स्रोत जल है।

सोलर कुकर द्वारा सौर ऊर्जा को ऊष्मा के रूप में एकत्रित करके इसे भोजन पकाने में । प्रयोग किया जाता है। सूर्य की प्रकाश किरणें कुकर के काँच के ढक्कन तथा परावर्तक पर पड़ती है। काँच के ढक्कन पर तथा परावर्तक से परावर्तित होकर आने वाली प्रकाश किरणें बाक्स में रखे बर्तन तथा उसकी भीतरी दीवारों पर पड़ती है। बर्तन की बाहरी सतह तथा बॉक्स की दीवारें व तली सभी काले रंग की होती हैं, जिससे सूर्य की किरणों की ऊर्जा को अवशोषित कर लिया जाता हैं परिणामस्वरूप बॉक्स के अन्दर का ताप बढ़ जाता है। दो तीन घंटों में इसके अन्दर रखा खाना पक जाता है। सोलर कुकर की सहायता से चपाती बनाने और सफाई करने के अतिरिक्त सभी प्रकार के भोजन पकाये जा सकते हैं।

जनसंख्या वृद्धि और दैनिक जीवन की विभिन्न आवश्यकताओं की पूर्ति के लिए ऊर्जा की माँग दिनों-दिन बढ़ रही है। वर्तमान में कुल ऊर्जा व्यय का 80% भाग पेट्रोलियम उत्पादों पर निर्भर है। जीवाश्म ईंधन अनवीकरणीय ऊर्जा के स्रोत हैं। यदि हम इसी प्रकार अनवीकरणीय ऊर्जा का अन्धाधुन्ध प्रयोग करते रहे, तो ये स्रोत एक दिन समाप्त हो जाएँगे। इस कारण ऊर्जा संकट उत्पन्न हो जाएगा।

ऊर्जा संकट को दूर करने के लिए हम नवीकरणीय ऊर्जा स्रोत जैसे- सूर्य, जल, वायु, बायोगैस आदि के प्रयोग पर जोर देंगे तथा निम्नलिखित उपायों पर अमल कराने का प्रयास करेंगे –

1. घर के विद्युत उपकरण जैसे- पंखे, बल्ब, हीटर आदि की आवश्यकता न होने पर बन्द रखना चाहिए।

2. जहाँ पर सम्भव हो, भोजन पकाने में, भोज्य पदार्थों के सुखाने में, पानी को गर्म करने में सौर ऊर्जा का ही प्रयोग करना चाहिए।

3. प्रकाश उत्पन्न करने के लिए ट्यूब लाइट, सोडियम वाष्प लैम्प/मरकरी वाष्प लैम्प का प्रयोग घरों में तथा सड़कों पर करना चाहिए।

4. कम दूरी के लिए पेट्रोल/डीजल के वाहनों का प्रयोग नहीं करना चाहिए।

5. ईंधन की कम खपत करने वाले वाहनों का प्रयोग करना चाहिए तथा इंजनों की सफाई करते रहना चाहिए।

6. ऊर्जा अपव्यय की रोकथाम और ऊर्जा बचत की उचित आदतों का ज्ञान होना चाहिए।

पृथ्वी पर ऊर्जा का सबसे बड़ा स्रोत सूर्य है।

नवीकरणीय ऊर्जा स्रोत जैसे सौर ऊर्जा, वायु ऊर्जा, जल ऊर्जा तथा बायोगैस से प्राप्त ऊर्जा पुनः प्राप्त होने वाले ऊर्जा के स्रोत है। विकास के साथ-साथ ऊर्जा की माँग में वृद्धि हुई है। अतः विभिन्न ऊर्जा स्रोतों का न्यायसंगत उपयोग किया जाना चाहिए। अनवीकरणीय ऊर्जा स्रोत समाप्त होते जा रहे हैं। अतः हमें नवीकरणीय ऊर्जा स्रोतों का अधिकाधिक उपयोग करना चाहिए।

बायोगैस मेथेन और कार्बन डाइऑक्साइड गैसों का मिश्रण है। यह गैस प्लांट में गोबर और जल के मिश्रण से उत्पन्न की जाती है। जब मिक्सिग टैंक में गोबर और जल को मिलाकर पाचक टैंक में डाला जाता है, तो मेथेन और कार्बन डाइऑक्साइड गैस उत्पन्न होती है। इस गैस को ही बायोगैस कहते हैं।

कोयला, पेट्रोलियम्।

सूर्य की ऊष्मीय ऊर्जा का उपयोग वायु ऊर्जा में, जल ऊर्जा में, प्रकाश संश्लेषण क्रिया में, सोलर कुकर, सोलर सेल, सौर जल ऊष्मक तथा सभी प्राणियों के भोजन में किसी-न-किसी रूप में होता है।

जल, पवन, जैव गैस तथा सूर्य ऊर्जा।

ऊर्जा संरक्षण हेतु निम्नलिखित उपायों को अपनाना चाहिए

• ऊर्जा अपव्यय की रोकथाम और ऊर्जा बचत की उचित आदतों का ज्ञान ऊर्जा बचत में सहायक हो सकता है।
• ऊर्जा संरक्षण के दृष्टिकोण से परम्परागत (अनवीकरणीय ऊर्जा स्रोतों का उपयोग यदाकदा ही करना उपयुक्त होगा।
• घर के विद्युत उपकरण जैसे पंखे, बल्ब, हीटर आदि को अति आवश्यक होने पर ही प्रयोग में लाना चाहिए। आवश्यकता न होने पर इनका उपयोग बन्द रखना चाहिए।
• जहाँ पर सम्भव हो भोजन पकाने में, भोज्य पदार्थों के सुखाने में, पानी को गर्म करने में सौर ऊर्जा का ही प्रयोग करना चाहिए।
• सोलर कुकर से भोजन पकाने पर आवश्यक तत्त्व भी सुरक्षित रहते हैं।
• प्रकाश उत्पन्न करने के लिए ट्यूब लाइट, सोडियम वाष्प लैम्प/मरकरी वाष्प लैंप का प्रयोग घरों में तथा सड़क पर करना चाहिए।
• भोजन पकाने के लिए प्रेशर कुकर का प्रयोग करना चाहिए, इससे ऊर्जा की बचत होती है।
• खाना पकाने में मिट्टी के तेल का प्रयोग करते समय अच्छे किस्म के स्टोव का प्रयोग करना चाहिए।
• आस-पास के स्थानों के आने जाने के लिए पेट्रोल/डीजल के वाहनों का प्रयोग नहीं करना चाहिए।
• व्यक्तिगत वाहनों के प्रयोग के स्थान पर यात्रा रेलगाड़ी/बस जैसे सार्वजनिक वाहनों से करनी चाहिए। ऐसा करने पर ईंधन की बचत होगी।

1. My legs are not as long as yours.

2. Tegumai ordered Taffy not to bother grown-ups.

1. idle × busy 

2. fake × genuine 

3. rudely × politely 

4. humble × haughty.

The author is telling us the story.

'Women Power’ – in Neolithic, Medieval and Present times

The position of women in society and the power they wield has changed through the ages. During the Neolithic Age, women spent their days gathering berries, roots, nuts, etc. They also gathered materials to make pots and weapons. Women stayed on the home front and looked after the children, but were thought to be equal to men. The men hunted and brought home the food. Later on, with the start of agriculture, women also began to farm and weave cloth.

Medieval society, however, was patriarchal, Women were to fall under male control, and regardless of class women had to submit to the male head of her household. Rural women had many domestic responsibilities, like caring for the children, preparing food and tending livestock. They also had to lend a hand in other household activities like grinding, brewing and spinning. During harvest time,, women often helped their husbands in the field to bring in the crops. However, slowly women were increasingly relegated to low-paying tasks like spinning. They suffered a lot of criticism, lacked freedom and stood nowhere next to men.

Today, around the world, women’s status in each society and culture varies. In some societies, women’s status improved gradually, while in other, it has declined or remained unchanged. This is due to the major changes that have taken place in areas such as legislations, education, employment, awareness of their rights on the part of women, etc. In some societies, women have emerged as major political leaders, statesmen, doctors, lawyers, etc. In some places, she is still subjected to inhuman cruelty, sexual exploitation, domestic violence, etc.

Tegumal wore very few clothes. He couldn’t read and write and he lived a happy life, except when he was hungry.

No, I don’t. I am very much a modern person and I wish to know how to do better in today’s environment. I like modern technology and the comforts it offers. Though I do like to understand evolution, I am not very interested in it.

According to Newton’s third law, to every action there is an equal and opposite reaction. So, when we kick a stone with much force, an equal and opposite reaction from the stone is applied on our legs which hurt our legs.

• When we apply pressure on a spring, it gets compressed.
• When we squeeze a rubber ball by allying force with our hands, it get compressed.

Emission of electrons from metal surface, when it is illuminated with light of suitable frequency is called photoelectric effect. 

Metals act as reducing agents because highly reactive metals have the ability to displace low reactivity metals from their compounds. Non-metals do not display this property.

Iodine and carbon are non-metals which are lustrous. Note that carbon is lustrous only in certain forms like diamond, and graphite.

(a) Metals form oxides (metallic oxides) which are basic in nature. Some examples are Na₂O, K₂O etc.

(b) Non-metals form oxides (non-metallic oxides) which are acidic in nature. Some nonmetallic oxides are NO₂, SO₂.

The answer is(c) Zinc

Galvanization is a process of applying a layer of Zinc on iron by using electrolysis.

The meaning of Ozone hole is Reduced Ozone concentration is the stratosphere..

Correct option: (B) Metabolism

Given, A = {1, 2, 3, … 9} and (a, b) R (c, d) if a + d = b + c for (a, b), (c, d) ∈ A ×A.

Let (a, b) R(a, b)

So, a + b = b + a, ∀ a, b ∈ A which is true for any a, b ∈ A.

Thus, R is reflexive.

Let (a, b) R(c, d)

Then,

a + d = b + c

c + b = d + a

(c, d) R(a, b)

Thus, R is symmetric.

Let (a, b) R(c, d) and (c, d) R(e, f)

a + d = b + c and c + f = d + e

a + d = b + c and d + e = c + f

(a + d) – (d + e = (b + c) – (c + f)

a – e = b – f

a + f = b + e

(a, b) R(e, f)

So, R is transitive.

Therefore, R is an equivalence relation.

Let f: A → B be many-one function.

Let f(a) = p and f(b) = p

So, for inverse function we will have f^-1(p) = a and f^-1(p) = b

Thus, in this case inverse function is not defined as we have two images ‘a and b’ for one pre-image ‘p’.

But for f to be invertible it must be one-one.

Now, let f: A → B is not onto function.

Let B = {p, q, r} and range of f be {p, q}.

Here image ‘r’ has not any pre-image, which will have no image in set A.

And for f to be invertible it must be onto.

Thus, ‘f’ is invertible if and only if ‘f’ is both one-one and onto.

A function f = X → Y is invertible iff f is a bijective function.

(i) A diamagnetic substance is attracted towards a region of weaker magnetic field.

(ii) (a) Permanent magnets are made of steel which is characterised by high retentivity and high coercivity. 

(b) Electro magnets are made of soft iron which is characterised by high retentivity and low coercivity.

-(27/125) 

= -(3√27/3√125) 

= 3√-(3 x 3 x 3)/(5 x 5 x 5)

= -(3/5)

125/216 = 3√125/216 = 3√((5 x 5 x 5)/(6 x 6 x 6))

= 5/6

Correct option : (4)

Explanation: 

Option (1), (2) and (3) are experimentally observed facts of the phenomenon of photoelectricity and are explained by Einstein’s theory of the photoelectricity. Option (4) refers to quantization of charge in general and is not a part of Einstein’s theory of photoelectric emission. 

-125 x 1000 = 3√(-125 x 100)

= 3√-(5 x 5 x 5) x (10 x 10 x 10)

= -5 x 10 = -50

Quantum theory of radiation (The photon picture of electromagnetic radiation) : 

(1) In its interaction with matter, electromagnetic radiation behaves as particles or quanta of energy. A quantum of energy is called a photon.

(2) If the frequency of radiation is v, irrespective of the intensity of radiation, each photon has energy hv and momentum hv/c, where c is the speed of light in free space.

(3) Intensity of radiation corresponds to the number of photons incident per unit time per unit surface area.

(4) Photons are electrically neutral and have zero rest mass.

(5) A photon particle collision (such as a photon-electron collision) obeys (he principles of conservation of energy arid momentum. However, in such a collision, an incident photon may be absorbed and/or a new photon may be created, so that the number of photons may not be conserved. For example, a γ-ray photon of energy greater than 1.02 MeV can produce an electron-positron pair in the presence of a heavy nucleus such as lead. In this case, the photon disappears and two particles (electron and positron) are produced. The total energy and momentum are conserved.

[Note: Photons have unit spin. Photons are influenced by gravitational field. A gravitational field can change the path and/or frequency/wavelength of a photon. Even after more than a century of its introduction, the concept of photon is not fully understood.]

Concept of quantization of energy:

Max Planck proposed quantum concept in 1900 in order to explain the thermal radiations emitted by a black body and the shape of its radiation curves. According to Planck, matter is composed of a large number of oscillating particles (atoms) which vibrate with different frequencies. Each atomic oscillator – which vibrates with its characteristic frequency – emits or absorbs electromagnetic radiation of the same frequency. It also says that

1. If an oscillator vibrates with frequency v, its energy can have only certain discrete values, given by the equation.

E_n = nhυ n = 1, 2, 3 ………..

where A is a constant, called Planck’s constant.

2. The oscillators emit or absorb energy in small packets or quanta and the energy of each quantum is E = hυ. 

This implies that the energy of the oscillator is quantized – that is, energy is not continuous as believed in the wave picture. This is called quantization of energy.

Correct option is (C) will depend on the shortest wavelength 

Correct option is (A) electron 

Moment of a force about a given point is the product of the force and the perpendicular distance of the point from the axis of rotation.

Angular velocity of a rigid body is the rate of change of angular displacement. Its unit is rads^-1 .

When force rotates the body in an anti-clockwise direction, moment of a force is positive.

Angular displacement of a rotating body is the angle described by a line in the body which is perpendicular to the axis of rotation. Angular displacement is measured in radians.

Two equal and opposite forces with some finite perpendicular distance between them constitute a couple of forces.

The rotating ability of the couple is called moment of the couple. It is measured by the product of the force and the arm of the couple.

Unit is Nm.

Dimension is M¹L²T^-2.

The algebraic sum of the moments of any number of forces about Any point is equal to the moment of their resultant about the same point.

Two equal unlike parallel forces acting at two different points on a rigid body constitute a couple. 

E.g.

• Pedalling a bicycle. 
• Spinning a top 
• Opening or closing a tap 
• Turning the steering wheel of a vehicle.

A body is said to have rotational motion if a line of points in the body remains fixed during the motion of the body. 

E.g.: 

• A spinning top 
• A rotating wheel

Resultant force of two like parallel forces R = P + Q. Where P and Q are the magnitudes of like parallel forces.

The condition of equilibrium of a body acted upon by a number of parallel forces is, 

1. Algebraic sum of the forces must be zero. i.e., Sum of the forces acting in the upward direction must be equal to the sum of the forces acting in the downward direction. 

2. The algebraic sum of the moments of the forces about any point in their plane must be zero. i.e., Sum of the moments of the forces about a point in the anticlockwise direction is equal to the sum of the moments of the forces about the same point in the clockwise direction.

When a system is in stable equilibrium it has minimum PE.

As \(\vec{L}=\vec{r}\times m\vec{v}\) i.e., magnitude of \(\vec{L}\) decreases but direction remains constant.