Why does the cord of an electric heater
[question] Question. Why does the cord of an electric heater not glow while the heating element does ? [/question] [solution] solution: The cord of an electric heater is made of thick copper wire and has much lower resistance than the heating element. For the same current (I) flowing through the cord and the element, heat produced in the element is much more than that produced in the cord. As a result, the element becomes very hot and glows whereas the cord does not become hot and as such does n...
Read More →List all the different social groups which joined the Non-Cooperation Movement of 1921.
[question] Question. List all the different social groups which joined the Non-Cooperation Movement of 1921. Then choose any three and write about their hopes and struggles to show why they joined the movement [/question] [solution] Solution: The different social groups that joined the Non-Cooperation Movement of 1921 were the urban middle class comprising lawyers, teachers and headmasters, students, peasants, tribals and workers. Peasants, tribals and workers joined the movement from the countr...
Read More →What do we call the gravitational force between the earth and an object ?
[question] Question. What do we call the gravitational force between the earth and an object ? [/question] [solution] Solution: It is called force of gravity [/solution]...
Read More →What is (a) the highest,
[question] Question. What is (a) the highest, (b) the lowest total resistance that can be secured by combinations of four coils of resistances $4 \Omega, 8 \Omega, 12 \Omega, 24 \Omega$ ? [solution] solution: (a) The highest resistance is secured when all the resistors are connected in series. The equivalent resistance is given by $R_{g}=4 \Omega+8 \Omega+12 \Omega+24 \Omega=48 \Omega$ (2) The lowest resistance is secured when all the four coils are connected in parallel. The equivalent resistan...
Read More →Compare the images of Bharat Mata in this chapter with the image of Germania in Chapter 1.
[question] Question. Compare the images of Bharat Mata in this chapter with the image of Germania in Chapter 1. [/question] [solution] Solution: The image of Bharat Mata as painted by Abanindranath Tagore shows her as bestowing learning, food and clothing. She bears aesthetic quality as denoted by the mala held by her. This is similar to the image of Germania as painted by Philip Veit, where she holds a sword, but looks more feminine. The other painting of Bharat Mata is more manly in its repres...
Read More →What is the acceleration of free fall ?
[question] Question. What is the acceleration of free fall ? [/question] [solution] Solution: The acceleration of free fall for object moving near the surface of earth is $9.81 \mathrm{~ms}^{-2}$. [/solution]...
Read More →Write a newspaper report on: (a) The Jallianwala Bagh massacre
[question] Question. Write a newspaper report on: (a) The Jallianwala Bagh massacre (b) The Simon Commission [/question] [solution] Solution: (a) The Jallianwala Bagh massacre—facts—on 13 April,1919, General Dyer blocked the exit points from the enclosed ground of Jallianwala Bagh where a large crowd had gathered—some to protest against the British government’s repressive measures, others to attend the annual Baisakhi fair. Dyer’s objective was to “produce a moral effect” and terrorise satyagrah...
Read More →How can three resistors of resistances
[question] Question. How can three resistors of resistances $2 \Omega, 3 \Omega$, and $6 \Omega$ be connected to give a total resistance of (a) $4 \Omega$ (b) $1 \Omega$ ? [/question] [solution] solution: (a) To get a total resistance of $4 \Omega$ from resistors of resistances $2 \Omega, 3 \Omega$ and $6 \Omega$, the resistors are joined as shown below. The resistors having resistances $3 \Omega$ and $6 \Omega$ are connected in parallel. This combination is connected in series with the resistor...
Read More →What is the importance of universal law of gravitation ?
[question] Question. What is the importance of universal law of gravitation ? [/question] [solution] Solution: Importance of universal law of gravitation is as follows : (i) It is the gravitational force between the Sun and the earth, which makes the earth move around the Sun. (ii) The tides formed in sea are because of gravitational pull exerted by the Sun and the Moon on the surface of water. (iii) It is the gravitational pull of earth, which keeps us and other bodies firmly on the ground. (iv...
Read More →What is meant by the idea of satyagraha?
[question] Question. What is meant by the idea of satyagraha? [/question] [solution] Solution: The idea of satyagraha implies a unique method of mass agitation that emphasises the power of truth, and the need to search for truth. It upholds the belief that if the cause is true and the fight is against injustice, then there is no need for physical force or coercion against the oppressor. Satyagraha is synonymous with non-violent agitation, where an appeal is made to the oppressor’s conscience to ...
Read More →What happens to the force between two objects, if
[question] Question. What happens to the force between two objects, if (i) the mass of one object is doubled ? (ii) the distance between the objects is doubled and tripled ? (iii) the masses of both objects are doubled ? [/question] [solution] Solution: (i) The force of gravitation doubles. (ii) The force of gravitation decreases 4 times if the distance between the objects is doubled, and if the distance between the objects is tripled then the force of gravitation decreases 9 times. (iii) The fo...
Read More →Explain: (a) Why growth of nationalism in the colonies is linked to an anti-colonial movement.
[question] Question. Explain: (a) Why growth of nationalism in the colonies is linked to an anti-colonial movement. (b) How the First World War helped in the growth of the National Movement in India. (c) Why Indians were outraged by the Rowlatt Act. (d) Why Gandhiji decided to withdraw the Non-Cooperation Movement. [/question] [solution] Solution: (a) Colonisation affected people’s freedom, and nationalist sentiments surged during the process of struggle against imperial domination. The sense of...
Read More →If the Moon attracts the earth, why does the earth not move towards the Moon ?
[question] Question. If the Moon attracts the earth, why does the earth not move towards the Moon ? [question] [solution] Solution: The earth does not move towards the Moon because the force exerted by the earth or the Moon on each other is insufficient to move the earth, on account of its huge mass....
Read More →What are the advantages of connecting electrical
[question] Question. What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series. [/question] [solution] solution: (a)In case of devices in parallel, if one device gets damaged (or open), all others will work as usual as the whole circuit does not break. This is not so with the devices connected in series because when one device fails, the circuit breaks and all devices stop working. (b)Since potential difference across all devices i...
Read More →The earth and the Moon are attracted to each other by gravitational force.
[question] Question. The earth and the Moon are attracted to each other by gravitational force. Is the force with which the earth attracts the Moon greater, smaller or the same as the force with which the Moon attracts the earth ? Why ? [question] [solution] Solution: The earth attracts the Moon with the same force with which the Moon attracts the earth because, the gravitational forces between any two bodies are equal and opposite (Newton's third law). [solution]...
Read More →Why did nationalist tensions emerge in the Balkans?
[question] Question. Why did nationalist tensions emerge in the Balkans? [/question] [solution] Solution: Nationalist tensions emerged in the Balkans because of the spread of ideas of romantic nationalism as also the disintegration of the Ottoman Empire that had previously ruled over this area. The different Slavic communities in the Balkans began to strive for independent rule. They were jealous of each other and every state wanted more territory, even at the expense of others. Also, the hold o...
Read More →How was the history of nationalism in Britain unlike the rest of Europe?
[question] Question. How was the history of nationalism in Britain unlike the rest of Europe? [solution] Solution: The history of nationalism in Britain was unlike that in the rest of Europe in the sense that it was forced down upon the masses. There was no concept of a British nation prior to the eighteenth century. The region was in fact inhabited by different ethnic groups (English, Welsh, Scot, Irish). Each group had its own cultural and political tradition. However, as the English state gre...
Read More →Through a focus on any two countries, explain how nations developed over the nineteenth century.
[question] Question. Through a focus on any two countries, explain how nations developed over the nineteenth century. [/question] [solution] Solution: The development of the German and Italian nation states in the nineteenth century Political fragmentation: Till the middle of the nineteenth century, the present-day nations of Germany and Italy were fragmented into separate regions and kingdoms ruled by different princely houses. Revolutionary uprisings: Nineteenth-century Europe was characterise...
Read More →Choose three examples to show the contribution of culture to the growth of nationalism in Europe.
[question] Question. Choose three examples to show the contribution of culture to the growth of nationalism in Europe. [/question] [solution] Solution: Apart from wars and territorial expansion, culture also played a crucial role in the development of nationalism. Romanticism was a European cultural movement aimed at developing national unity by creating a sense of shared heritage and common history. The Romantic artists' emphasis on emotions, intuition and mystical feelings gave shape and expre...
Read More →What is the magnitude of the gravitational force between the earth
[question] Question. What is the magnitude of the gravitational force between the earth and a $1 \mathrm{~kg}$ object on its surface? (Mass of the earth is $6 \times 10^{24} \mathrm{~kg}$ and radius of the earth is $6.4 \times 10^{6} \mathrm{~m}$.) [/question] [solution] Solution: $\mathrm{F}_{\mathrm{g}}=\frac{\mathrm{G} \times \mathrm{M} \times \mathrm{m}}{\mathrm{R}^{2}}$ Where, M = mass of the earth ; m = mass of object; R = radius of earth. $\mathrm{F}_{8}=\frac{6.67 \times 10^{-11} \times\...
Read More →Judge the equivalent resistance
[question] Question. Judge the equivalent resistance when the following are connected in parallel (a) $1 \Omega$ and $10^{6} \Omega$ (b) $1 \Omega, 10^{3} \Omega$ and $10^{6} \Omega$. [/question] [solution] solution: (a) Approx. $1 \Omega$ (slightly less than $1 \Omega$ ) as other one $\left(10^{6} \Omega\right)$ is very large as compared to $1 \Omega$. In parallel combination of resistors, the equivalent resistance is lesser than the least resistance (in this case, $1 \Omega$ ). (b)Again, resis...
Read More →Explain what is meant by the 1848 revolution of the liberals
[question] Question. Explain what is meant by the 1848 revolution of the liberals. What were the political, social and economic ideas supported by the liberals? [/question] [solution] Solution: The 1848 revolution of the liberals refers to the various national movements pioneered by educated middle classes alongside the revolts of the poor, unemployed and starving peasants and workers in Europe. While in countries like France, food shortages and widespread unemployment during 1848 led to popular...
Read More →Gravitational force acts on all objects in proportion to their masses.
[question] Question. Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object ? [/question] [solution] Solution: A freely falling object of any mass falls under the action of gravity given by $g=\frac{G M}{r^{2}}$, where $^{\prime} G^{\prime}$ is constant of gravitation, M is mass of earth, r is the distance between the object and the centre of earth. Thus, the acceleration due to gravity is independent of the mass o...
Read More →Redraw the circuit of Q. 1,
[question] Question. Redraw the circuit of Q. 1, putting in an ammeter to measure the current through the resistors and a voltmeter to measure the voltage across the 12 ohm resistor. What would be the readings in the ammeter and the voltmeter ? [/question] [solution] solution: Since all the three resistances are in series, total resistance in the circuit, $R=5+8+12=25 \Omega$ Current in the circuit, $\mathrm{I}=\frac{\mathrm{V}}{\mathrm{D}}=\frac{2+2+2}{25}=\frac{6}{25}=0.24 \mathrm{~A}$, thus, ...
Read More →What changes did Napoleon introduce to make the administrative system more efficient in the territories ruled by him?
[question] Question. What changes did Napoleon introduce to make the administrative system more efficient in the territories ruled by him? [/question] [solution] Solution: Napoleon introduced several changes to make the administrative system more efficient in the territories ruled by him. He formulated the Civil Code of 1804, also known as the Napoleonic Code. It did away with privileges based on birth. This law established equality before law, and also secured the right to property. Napoleon sh...
Read More →