HBSE Class 10 Science Question Paper 2022 Answer Key

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HBSE Class 10 Science Question Paper 2022 Answer Key

Q1.(a) What is a solenoid ? Draw the magnetic field around the current carrying solenoid.

Ans. Solenoid– A solenoid is a coil which is made of an insulated wire wound in the form of a cylinder usually made of solid iron, solid steel, or powdered iron which produces magnetic field when electrical phenomenon is suffered through it and behaves as a magnet.

(b) Write the Fleming’s right-hand rule.

Ans. Fleming’s Right Hand Rule states that if we arrange our thumb, forefinger and middle finger of the right-hand perpendicular to each other, then the thumb points towards the direction of the motion of the conductor relative to the magnetic field, the forefinger points towards the direction of the magnetic field and the middle finger points towards the direction of the induced current.

OR

Explain principle and working of an electric motor by drawing a labelled diagram.

Ans. Principle– An electric motor is a rotating device that converts electrical energy to mechanical energy working.

Working– Current in the coil ABCD enters from the source battery through conducting brush X and flow back to the battery through brush Y. Notice that the current in the arm AB of the coil flows from A to B. In arm CD it flows from C to D that is opposite to the direction of current through arm AB on applying Fleming’s left hand rule for the direction of force on a current-carrying conductor in a magnetic field. We find that the force acting on arm AB pushes it downwards while the force acting on arm CD pushes it upwards. Thus the coil and the Axle O, mounted free to turn about an axis, rotate anti-clockwise at half rotation. Q makes contact with the brush X and P with brush Y. Therefore the current in the coil gets reversed and flows along the path DCBA. The reversal of current also reverses the direction of force acting on the two arms AB and CD. Thus the arm AB of the coil that was earlier pushed down, is now pushed up and the arm CD previously pushed up is pushed down. There is a continuous rotation of the coil and to the axle.

Q2. Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?

Ans. Coils of electric toasters and electric irons made of an alloy rather than a pure metal because the resistivity of an alloy is higher than the pure metal. At high temperatures, the alloys do not melt easily. Alloys are harder than pure metals.

Q3. Write the difference between convex mirror and concave mirror.

Ans. Convex Mirror– The outer surface of the spherical mirror is reflecting. It forms virtual and erect images. The image formed is always smaller than the actual size. Its focus point lies at behind its reflecting surface.

Concave Mirror– The inner surface of the spherical mirror is reflecting. It forms a real-inverted image and also virtual-erect pictures. The image formed can be larger or smaller than the actual size. Its focus point lies at the front of its reflecting surface.

Q4. Nitrogen (atomic number 7) and Phosphorus (atomic number 15) belong to group 15 of periodic table. Write electronic configurations of these two elements. Which of these will be more electronegative and why ?

Ans. The electronic configuration of nitrogen N(7)=2,5 and Phosphorous P(15)=2,8,5 . Nitrogen is more electronegative than Phosphorus. From top to bottom a group, electronegativity decreases. This is because number of shell increases down a group, and thus there is an increased distance between the valence electrons and nucleus, or a greater atomic radius. Nitrogen has a smaller atomic radius than Phosphorus, the attraction of its nucleus towards the incoming electron is more than phosphorus. Therefore, nitrogen accepts electrons more easily.

OR

(a) How does atomic size vary in a period? Explain.

Ans. Atomic size is the distance between the center of nucleus and the outermost electron in the outer shell. Across a period from left to right there is decrease in atomic size with increase in nuclear charge of the element. Atomic size increases down the group because of addition of extra shell.

(b) In modern periodic table, which are the metals among first ten elements?

Ans. In the modern periodic table, Lithium(Li) and Beryllium(Be) are the only metals among the first 10 elements.

Q5. Define decomposition reaction. Write a balanced equation for decomposition reaction.

Ans. Decomposition Reaction– A decomposition reaction can be defined as a chemical reaction in which one reactant breaks down into two or more products. The general representation of decomposition reaction is AB → A + B , Where AB = Reactant, A and B = Product molecules

eg. H2CO3 → H2O + CO2

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