How does the force of gravitation between two objects
[question] Question. How does the force of gravitation between two objects change when the distance between them is reduced to half ? [/question] [solution] Solution: When all other variables remain constant, the force of gravitation is inversely proportional to the square of distance between the two objects. $F \propto \frac{1}{r^{2}} \Rightarrow \frac{F^{\prime}}{F}=\frac{r^{2}}{\left(\frac{r}{2}\right)^{2}}=\frac{4 r^{2}}{r^{2}}=4$ $\therefore$ The force of gravitation increases 4 times. [sol...
Read More →Draw a schematic diagram of a circuit consisting of a battery
[question] Question. Draw a schematic diagram of a circuit consisting of a battery of three cells of $2 \mathrm{~V}$ each, a 5 ohm resistor, an $8 \mathrm{ohm}$ resistor, and a $12 \mathrm{ohm}$ resistor, and a plug key, all connected in series. [/question] [solution] solution: [/solution]...
Read More →Briefly trace the process of German unification.
[question] Question. Briefly trace the process of German unification. [question] [solution] Solution: The process of German unification was continued by Prussia after the defeat of the liberal, middle-class Germans at the hands of the aristocrats and the military in 1848. Its chief minister Otto von Bismarck carried out this process with the help of the Prussian army and bureaucracy. Over seven years, Prussia fought three wars with Austria, Denmark and France. These wars culminated in Prussian v...
Read More →(a) Which among iron and mercury is a better conductor?
[question] Question. (a) Which among iron and mercury is a better conductor? Given, $\rho_{\text {iron }}=10.0 \times 10^{-8} \Omega \mathrm{m}$ and $\rho_{\text {mercury }}=94.0 \times 10^{-8} \Omega \mathrm{m}$ (b) Which material is the best conductor ? [/question] [solution] solution: (a) Iron is a better conductor than mercury as resistivity $(\rho)$ for iron is less than that for mercury. (b) Silver is the best conductor because its resistivity $(\rho)$ is least. [/solution]...
Read More →You have a bag of cotton and an iron bar,
[question] Question. You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why ? [solution] Solution: A weighing machine measures the apparent weight of an object. We know that apparent weight $\left(\mathrm{W}_{2}\right)$ is equal to true weight $\left(\mathrm{W}_{2}\right)$ minus buoyant force $\left(\mathrm{F}_{\mathrm{B}}\right)$ i.e., $\mathrm{W}_{\mathrm{a}}...
Read More →Who were Marianne and Germania? What was the importance of the way in which they were portrayed?
[question] Question. Who were Marianne and Germania? What was the importance of the way in which they were portrayed? [/question] [solution] Solution: Marianne and Germania were respective female allegories for the French and the German nation. They stood as personifications of ideals like 'liberty' and 'the republic'. The importance of the way in which they were portrayed lay in the fact that the public could identify with their symbolic meaning, and this would instil a sense of national unity ...
Read More →What steps did the French revolutionaries take to create a sense of collective identity among the French people?
[question] Question. What steps did the French revolutionaries take to create a sense of collective identity among the French people? [/question] [solution] Solution: The French revolutionaries took many important steps to create a sense of collective identity among the French people. Ideas of la patrie (the fatherland) and le citoyen (the citizen) popularised the notion of a united community enjoying equal rights under a constitution. A new French flag replaced the royal standard. The Estates G...
Read More →You find your mass to be 42 kg
[question] Question. You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg ? [/question] [solution] Solution: When you weigh your body, an upward buoyant force acts on your body due to the air (a fluid) present around you. As a result, the body gets pushed slightly upwards, causing the weighing machine to show a reading slightly less than the actual value. [/solution]...
Read More →Why are coils of electric toasters and electric irons
[question] Question. Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal ? [/question] [solution] solution: This is because (i) resistivity of an alloy is generally higher than that of pure metals (ii) an alloy does not oxidise at high temperatures. [/solution]...
Read More →Why does an object float or sink when placed on the surface of water ?
[question] Question. Why does an object float or sink when placed on the surface of water ? [/question] [solution] Solution: If the density of an object is more than the density of the liquid, then it sinks in the liquid. This is because the buoyant force acting on the object is less than the weight of the object. If the density of the object is less than or equal to the density of the liquid, then it floats on the surface of the liquid. This is because the buoyant force acting on the object is ...
Read More →Write a note on: (a) Guiseppe Mazzini (b) Count Camillo de Cavour
[question] Question. 1. Write a note on: a) Guiseppe Mazzini b) Count Camillo de Cavour c) The Greek war of independence d) Frankfurt parliament e) The role of women in nationalist struggles [/question] [solution] Solution: (a) Guiseppe Mazzini: He was an Italian revolutionary who played a significant role in promoting the idea of a unified Italian state. He believed that nations were the natural units of mankind, and so Italy (which was then divided into a number of small states and kingdoms) h...
Read More →Let the resistance of an electrical component remain constant
[question] Question. Let the resistance of an electrical component remain constant while the potential difference across the two ends of the component decrease to half its former value. What change will occur in the current through it ? [/question] [solution] solution: We know that $I=V / R$, when potential difference becomes $V / 2$, and resistance remains constant, then, current becomes $1 / 2$ of its former value. [/solution]...
Read More →Does current flow more easily through a thick wire
[question] Question. Does current flow more easily through a thick wire or a thin wire of the same material when connected to the same source ? Why ? [/question] [solution] solution: The current flows more easily through a thick wire than through a thin wire. This is because, the resistance R of a thick wire (large area of cross-section) is less than that of a hin wire (small area of cross-section) as $\mathrm{R} \propto \frac{1}{\mathrm{~A}}$. [/solution]...
Read More →What do you mean by buoyancy ?
[question] Question. What do you mean by buoyancy ? [/question] [solution] Solution: The tendency for an immersed body to be lifted up in a fluid, due to an upward force that acts opposite to the action of gravity is called buoyancy [/solution]...
Read More →On what factors does the resistance
[question] Question. On what factors does the resistance of a conductor depend ? [/question] [solution] solution: The resistance $(R)$ of a conductor depends upon (1) Its length $(\ell): \mathrm{R} \propto \ell$ (2) Its cross-sectional area (A): $R \propto \frac{1}{A}$ (3) Nature of material i.e., resistivity $(\rho)$ of its material: $R \propto \rho$ (4) Temperature: more the temperature, more will be its resistance. [/solution]...
Read More →Why is it difficult to hold a school bag having a strap made of a thin and strong string ?
[question] Question. Why is it difficult to hold a school bag having a strap made of a thin and strong string ? [question] [solution] Solution: It is difficult to hold a school bag having a thin strap because the pressure on the shoulders is quite large. This is because the pressure is inversely proportional to the area on which the force acts. The smaller is the area, the larger will be the pressure on the surface. In the case of a thin strap, the contact area is very small. Hence, the pressure...
Read More →How much energy is given to each coulomb
[question] Question. How much energy is given to each coulomb of charge passing through a 6 V battery ? [/question] [solution] solution: Work done, $\mathrm{W}=\mathrm{QV}$ where $\mathrm{Q}=1 \mathrm{C} ; \mathrm{V}=6 \mathrm{~V}$ $\mathrm{W}=1 \mathrm{C} \times 6 \mathrm{~V}=\mathbf{6} \mathbf{J}$ [/solution]...
Read More →Why is the weight of an object
[question] Question. Why is the weight of an object on the Moon $\frac{1}{6}$ th of its weight on the earth ? [/question] [solution] Solution: Acceleration due to gravity $\left(\mathrm{g}_{\mathrm{m}}\right)$ on Moon is $\frac{1}{6}$ th of the acceleration due to gravity $\left(\mathrm{g}_{\mathrm{e}}\right)$ on earth. i.e., $\mathrm{g}_{\mathrm{m}}=\frac{1}{6} \mathrm{~g}_{\mathrm{e}}$ or $m g_{\mathrm{m}}=\frac{1}{6} \mathrm{mg}_{\mathrm{e}} \quad$ where, $\mathrm{m}=$ mass of object or $\qua...
Read More →What is meant by saying that the potential
[question] Question. What is meant by saying that the potential difference between two points is 1 V ? [/question] [solution] solution: Potential difference between two points is 1 volt if 1 joule of work is done to carry a charge of 1 coulomb from one point to the other. [/solution]...
Read More →Read the passage below:
[question] Question. Read the passage below: Nannu is a daily wage earner. He lives in Welcome Mazdoor Colony, a slum habitation in East Delhi. He lost his ration card and applied for a duplicate one in January 2004. He made several rounds to the local Food & Civil Supplies office for the next three months. But the clerks and officials would not even look at him, leave alone do his job or bother to tell him the status of his application. Ultimately, he filed an application under the Right to Inf...
Read More →Name a device that helps to maintain a potential
[question] Question. Name a device that helps to maintain a potential difference across a conductor. [/question] [solution] solution: A battery can be used to maintain a potential difference across a conductor. [/solution]...
Read More →Calculate the number of electrons constituting
[question] Question. Calculate the number of electrons constituting one coulomb of charge. [/question] [solution] solution: Number of electrons constituting 1 coulomb is given by, $\mathrm{n}=\frac{\mathrm{Q}}{\mathrm{e}}$ Where, $\mathrm{Q}=1 \mathrm{C}$ and $\mathrm{e}=$ charge of a single electron $=1.6 \times 10^{-19} \mathrm{C}$ or $\mathrm{n}=\frac{1 \mathrm{C}}{1.610^{-19} \mathrm{C}}=6.24 \times 10^{18}$ electrons. [/solution]...
Read More →Studies on political and social inequalities in democracy show that
[question] Question. Studies on political and social inequalities in democracy show that Α. democracy and development go together Β. inequalities exist in democracies C. inequalities do not exist under dictatorship D. dictatorship is better than democracy [/question] [solution] Solution: Β. inequalities exist in democracies [/solution]...
Read More →Define the SI unit of current.
[question] Question. Define the SI unit of current. [/question] [solution] solution: The SI unit of current is ampere (A). Current flowing through a conductor is said to be 1 ampere if 1 coulomb of charge flows through it in 1 second. [/solution]...
Read More →What are the differences between the mass of an object and its weight ?
[question] Question. What are the differences between the mass of an object and its weight ? [/question] [solution] Solution: [/solution]...
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