# HBSE Class 10 Science Question Paper 2019 Answer Key

HBSE Class 10 Science Question Paper 2019 Answer Key

HBSE Class 10 Science Previous Year Question Paper with Answer. HBSE Board Solved Question Paper Class 10 Science 2019. HBSE 10th Question Paper Download 2019. HBSE Class 10 Science Paper Solution 2019. Haryana Board Class 10th ScienceQuestion Paper 2019 Pdf Download with Answer.

SET-A

Q1. The blue colour of sky is due to :

(A)  Reflection of light

(B) Scattering of light

(C) Dispersion of light

(D) Refraction of light

Ans. (B) Scattering of light

Q2. Which of the following is not an example of a biomass energy source ?

(A) Wood

(B) Gobar gas

(C) Nuclear energy

(D) Coal

Ans. (C) Nuclear energy

Q3. What type/nature of image is formed by the eye lens at retina ?

Ans. Human eye lens are convex in nature and form real and inverted images.

Q4. On what factors the resistance of conductor depends ?

Ans. Resistance of conductor depends on-

(i) Length of the wire

(ii) Area of cross-section of the wire

(iii) Nature of material of the wire.

Q5. What are the disadvantages of fossil fuel ? Explain in brief.

Ans. The burning of coal and petroleum produces a lot of pollutants, causing air pollution. Fossil fuels release oxides of carbon, nitrogen, sulphur, etc., that cause acid rain, affecting soil fertility and potable water. The burning of fossil fuels produce gases such as carbon dioxide that causes global warming.

Q6. How can three resistors of resistance 2 Ω, 3 Ω, and 6 Ω be connected to give a total resistance   of  4 Ω ?

Ans. We can get a total resistance of 4Ω by connecting the R1= resistance in series with the parallel combination of R2=3Ω and R3=6Ω. When Resistance in parallel then

1/RP = 1/R2 + 1/R3 = 1/3 + 1/6 = 1/2

R =

Resistance in series :

RS = R + R1 = 2Ω + 2Ω = 4Ω

Q7. What are the advantages of water stored in the ground ?

Ans. advantages of water stored in the ground-

(i) It does not evaporate

(ii) It recharges wells near the area

(iii) It provides moisture to the vegetation

(iv) It does not provide breeding grounds for mosquitos , like stagnant water in lakes and ponds

(v) It is relatively protected from contamination by animal and human waste.

Q8.(a) Light enters from air to glass having  refractive index 1.50. What is the speed of  light in glass ? The speed of light in vacuum is 3 × 10⁸ ms-¹.

Ans. Refractive index μ = 1.50,  Speed of light c=3×10⁸ m/s, we know that  μ = c/v

v = c/μ = 3×10⁸/1.50 = 2 × 10⁸ m/s

Hence, the speed of light in glass is 2×10⁸ m/s.

(b) An object is situated at a position in between the main focus (F) and 2 F of a Convex lens. Draw the ray diagram showing the position, size and nature of image formed.

Ans. A ray from infinity i.e. parallel to principal axis of pole falls on lens and passes through focus of lens after refraction. Another ray falls on the pole of lens & passes without any deviation. Image is formed where two refracted rays intersect each other.

Position of image – image is beyond 2F

Size of image – more than size of object

Nature of image – image is inverted

Q9. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes ?

Ans. Principle– In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. It is working on the principle of electromagnetic induction.

Working– When the axle attached to the two rings is rotated such that the arm AB moves up (and the arm CD moves down) in the magnetic field produced by the permanent magnet. Let us say the coil ABCD is rotated clockwise in the arrangement. By applying Fleming’s right hand rule, the induced currents are set up in these arms along the directions AB and CD. Thus an induced current flows in the direction ABCD. If there are larger number of turns in the coil, the current generated in each turn adds up to give a large current through the coil. This means that the current in the external circuit flows from B2 to B1. After half a rotation, arm CD starts moving up and AB moving down. As a result, the directions of the induced currents in both the arms changes, giving rise to the net induced current in the direction DCBA. The current in the external circuit now flows from B1 to B2. Thus after every half rotation the polarity of the current in the respective arms changes. There are two brushes and in the electric generator, one brush is at all times in contact with the arm moving up in the field, while the other is in contact with the arm moving down. Because of these Brushes unidirectional current is produced.

Function of brushes is to transfer the current from coil to load connected in the circuit of the electric generator.

OR

(a) What is the Fleming’s Left-Hand Rule ? Explain.

Ans. When a current-carrying conductor is placed in an external magnetic field, the conductor experiences a force perpendicular to both the field and to the direction of the current flow. It was invented by John Ambrose Fleming.

(b) What do you mean by electromagnetic induction ? Explain the use of Fleming’s right-hand rule in finding the direction of current induced in the conductor.

Ans. Electromagnetic Induction (EMI) is a current produced because of voltage production (electromotive force) due to a changing magnetic field. This either happens when a conductor is placed in a moving magnetic field (when using an AC power source) or when a conductor is constantly moving in a stationary magnetic field.

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.

Q10. Which reactant is Oxidized in the following chemical reaction ?

CuO + H2 → Cu + H2

Ans. Hydrogen is oxidized and Copper is reduced.

Q11. You have three solutions A, B and C whose pH value is 4, 7 and 10 respectively. Out of above solutions, which solution is acidic ?

Ans. Solution A is acidic (pH=4). We know that If pH<7 then Acidic, If pH=7 then Neutral, If pH>7 then Basic.

Q12. Element M forms a Chloride with formula MCl. Element M would be most likely in the same group of Periodic table as  :

(A) Si

(B) Al

(C) Na

(D) Mg

Ans. (C) Na

Q13. What do you mean by displacement reactions ? Give one example (Chemical equation).

Ans. The reaction in which one element displaces or remover another element from its solution is called displacement reaction.

eg.  Zn + CuSO4 → ZnSO4 + Cu

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