## Friction Experiment Viva Questions

Coefficient of Friction Experiment Viva Questions and Answers

1. What is meant by friction?

Friction is an opposing force that comes into effect when a body moves or even tries to moves over another body’s surface.

2. Name the different types of friction.

(i). Static friction, (ii) limiting friction and (iii) kinetic friction

## Frequency of AC Mains using Sonometer Viva Questions

Frequency of AC Mains using Sonometer Experiment Viva Questions with Answers

1 Which is more dangerous in use a.c. or d.c.? Why?

Ans: For example, a 220V a.c has a peak value of 220 x 2 = 311 V whereas the peak value of a 220 d.c. is 220 V itself. Hence a.c. is more dangerous than d.c. of the same voltage.

## Newton's Law of Cooling Viva Questions

Viva Questions on Newton's Law of Cooling Experiment

1. What is meant by internal energy?

Ans: The sum of kinetic and potential energies of a body is called its internal energy.

2. Define temperature.

Ans: Temperature of a body is called as the degree of coldness or hotness of the body.

3. State Newton's law of cooling

Ans: The Newton's law of cooling is defined as the rate of decrease in heat from a body is directly proportional to the mean temperature difference between the body and its surroundings.

4. What is meant by thermodynamics?

Ans: Thermodynamics is a branch of science which deals with the study of transformation of heat energy into mechanical energy and vice-versa.

5. What is absolute zero of temperature?

Ans: —273.15° C

6. What is the tripple point temperature of water?

Ans: 273.16° K or 0.01°C

7. Define isothermal process.

Ans: Isothermal process is a physical change in which pressure and volume of a system change at constant temperature (It is a slow process).

Ans: Adiabatic process is a physical change in which pressure, volume and temperature change (It is a sudden process).

9. What is meant by irreversible process?

Ans: Any process that can't be retraced in the reverse order and in the opposite sense is called an irreversible process.

10. What is meant by reversible process?

Ans: A reversible process which can be made to proceed in two opposite directions with the same case, so that the system and the surroundings pass through exactly the same intermediate state as in the direct process.

11. Name the different modes of transmission of heat.

Ans: There are three modes of transmission of heat. They are conduction, radiation and convection.

Ans: Radiation is energy or particles that origins from a source and travels through space or other medium. It may be able to go through various materials.

eg: Light, X-ray, Sound, Microwaves and so on

13. What is Stefan-Boltzmann law?

Ans: Stefan-Boltzmann law states that the total radiant heat power emitted from a surface is directly proportional to the fourth power of the black body’s absolute temperature.

ie, j* = σT4

14. Define emissivity (or relative emittance) of a surface.

Ans: Emissivity (ε) is defined as the relative ability of a surface to emit heat by radiation. It is the ratio of radiant energy from an object’s surface at given temperature to the radiant energy of a black body at same temperature.

15. State Kirchhoff's law.

Ans: Kirchhoff's law of radiation states that at thermal equilibrium, the power radiated by an object is equal to the power absorbed by that object.

16. What is the velocity of heat radiation?

Ans: Thermal radiation or Heat radiation is the energy transfer in the form of electromagnetic waves. The velocity of thermal radiation in the vacuum is same as that of light.

c0 = n0c

where, c0 = thermal radiation velocity

n0 = refractive index of medium

c = wave velocity

17. To which part of the electromagnetic spectrum do the thermal radiation belong?

Ans: Infrared region

18. What is a black body?

Ans: A black body is a surface that absorbs all radiant energy falls on it, regardless of frequency or angle of incidence.

19. What is meant by black body radiation?

Ans: Blackbody radiation is defined as the spectrum of light emitted by any heated object. It is the radiation emitted by the black body. For example, filament of a light bulb

20. What is Wien's displacement law?

Ans: The wavelength at which the maximum radiated power for a blackbody is inversely proportional to the absolute temperature.

ie, λmax = b/T

b = constant of proportionality

T = absolute temperature

21. Aim of Newton’s law of Cooling

Ans: To study the connection of temperature of a body to the time as it cools by radiating heat.

22. Apparatus of Newton’s law of Cooling

Ans: Calorimeter and stirrer, thermometer, clamp and stand, stop-watch, hot water and so on

23. Principle of Newton’s law of Cooling

Ans: By Newton's law of cooling, rate of cooling is directly proportional to mean temperature difference between the cooling substance (water) and the surrounding.

i.e., dθ/dt (θ-θ0)

where, θ - mean temperature of the cooling substance (water)

θ0 - temperature of the surrounding

As time increases, θ decreases, (θ-θ0) decreases and hence rate of fall of temperature dθ/dt also decreases.

24. Procedure of Newton’s law of Cooling

Ans: About 2/3 rd of the calorimeter is filled with hot water of about 110°C. A thermometer is suspended inside the calorimeter from a clamp and stand. Let θ0 be the temperature of the surrounding. Water is stirred continuously to make it cool uniformly. When the temperature of hot water falls to 100°C, a stop-watch is started. For every one minute the temperature is noted. The time-temperature observation is continued till the temperature falls to say 20°C.

A graph is plotted with time along the X-axis and temperature θ along the Y-axis, The graph is known as cooling-curve of the liquid.

## Young's Modulus Experiment Viva Questions

Viva Questions on Young's Modulus Experiment

1. What is meant by stress?

Ans: Stress is defined as the restoring force that is acting per unit area of a body.

2. What is meant by strain?

Ans: Strain is defined as the ratio of change in dimension to the original dimension.

3. What is the unit of stress?

Ans: Nm-2

4. What is the unit of strain?

Ans: No unit.

5. Define elasticity.

Ans: The property of a body to recover its original pattern when the deforming forces are removed is called elasticity.

6. Who was the first man to investigate the stretching of metals?

Ans: Robert Hooke

7. State Hooke's law.

Ans: Within the elastic limit, the stress grown is directly proportional to the strain created in a body.

8. Which is more elastic either steel wire or rubber wire of same diameters and lengths?

Ans: Steel wire

9. What is meant by Young's Modulus of elasticity?

Ans: The ratio between the normal stress to the longitudinal strain in elastic limit is called as Young's modulus of elasticity.

10. What is the unit of elastic limit?

Ans: Nm-2

11. Distinguish between stress and pressure.

Ans: The restoring force acting per unit area is Stress and the amount of force applied per unit area is Pressure.

12. What is meant by elastic limit?

Ans: The maximum stress for a body can withstand before the permanent deformation of size or shape.

13. What is the modulus of elasticity?

Ans: The relationship (ratio) between stress and strain is called as Modulus of Elasticity (Young's modulus of elasticity).

λ = stress/strain

14. What are the different moduli of elasticity?

Ans: (i) Young's modulus,

(ii) Shear modulus, and

(iii) Bulk modulus.

15. What is the unit of modulus of elasticity?

Ans: Nm-2 or Pa

16. Why do you use a micrometer or vernier instead of a metre scale to measure the increase in length of the wire?

Ans: It is because the vernier can slide freely against the main scale.

17. What is elastic hysteresis?

Ans: Elastic Hysteresis is the difference between the strain energy and stress energy. It is the lagging of strain behind the stress.

18. Aim of Young's Modulus Experiment

Ans: To find out the Young's modulus of the material for a given wire by Searle's apparatus.

19. Apparatus of Young's Modulus Experiment

Ans: The Searl's apparatus, weight hanger, slotted weights, screw gauge, metre rule etc. The Searl's apparatus consists of two long metal wires AB and CD each of length about 2 m suspended side by side from a rigid support. AB is the experimental wire whose Young's modulus is to be determined. CD is the observation wire. The experimental wire AB carries a vernier V and the observation wire CD carries a main scale S. The vernier can slide freely against the main scale. The observation wire is made taut by suspending a load W at the lower end of the main scale.

20. Procedure of Young's Modulus Experiment

The length L of the experimental were from the support to the point of attachment to the vernier is measured by a metre rule. The radius r of this wire is measured with a screw gauge. The Young's modulus of the material of the wire AB is calculated by the equation. Y = MgL/πr2l = Lg/πr2 x (M/l)

## Atoms and Molecules Viva Questions

ATOMS AND MOLECULES VIVA QUESTIONS (CLASS 9)

1. What is the Avogadro number of Helium (He) atoms weigh ?

Ans: 4.0 g

2. Determine the number of hydrogen atoms in 3 mole of NH3 ?

Ans: 9 x 6.02 x 1023

3. Which of the following weighs least among  the following?

(a) 0.224 litres of O2 at NTP

(b) 6.02 x 1023 molecules of oxygen

(c) 6.02 x 1023 atoms of carbon

(d) 10 g of CO2

Ans: 0.224 litres of O2 at NTP

4. An element's oxides contain 57.1 % and 72.1 % oxygen, respectively. What is the second oxide if the first oxide is MO?

Ans: MO2

5. What is the molarity of Na2CO3 solution containing 10.6 g per 500 ml solution?

Ans:  0.2

6. Determine the volume of 0.5 M HNO3 that can be prepared from 25 mL of 2.5 M HNO3

Ans: 125 mL

7. If 30 L is converted into SI unit and expressed in scientific notation,  determine the value obtained?

Ans:  3 x 10-2 m3

8. The average density of earth is 5.5 g cm-3. In kg m-3, determine the average density?

Ans: 5.5 x 10-3

9.  In 1.0046, how many significant figures are there?

Ans:  five

10. From the given lists, which of the following has more number of rnolecules ?

(a) 1 g CO2

(b) 1 g N2

(c) 1 g H2

(d) 1 g CH4

Ans: 1 g H2

11. Carbon monoxide and carbon dioxide may be taken as examples for illustrating which  law ?

Ans: Law of multiple proportions

12. From the given, which of the following contains Avogadro number of atoms,

(a) 11.2 L of H2 at STP

(b) 32 g of oxygen

(c) 28 g nitrogen

(d) 22.4 L of Cl2 at STP

Ans: 11.2 L of H2 at STP

13. Find the volume of oxygen at STP required to react with 3 g graphite to give CO2  ?

Ans: 5.6 L

14. A solute has a molecular mass of 60 g and 90 g of it is dissolved in a litre of solution. Then what is its molarity?

Ans: 1.5

15. From the given samples, determine which of the following is not a mixture?

(a) air (b) milk (c) smoke (d) water

Ans: Water

16. The volume of l g of a gas at STP is 1.12 L. What will be its molecular mass ?

Ans: 20

17. A mass of 16 g of an element was mixed with 32 g oxygen when 32 g of compound was formed. If the element was the limiting reagent, what will be the mass ratio of the element to oxygen in the compound ?

Ans:  1:1

18. Chemical equations are balanced so that they are in accordance with which law?

Ans: Law of conservation of mass

19. At NTP, 0.225 g of carbon reacts with 140 mL of oxygen. What would the compound's molecular formula be then?

Ans: C3O2

20. 0.25 g of a tetratomic element is 3.125 x 10-3 mole. Then what is the atomic mass of the element is

Ans:  20

21. Neon contains two isotopes of atomic masses 20 and 22 in the mass ratio 9 : 1  respectively. Find the atomic mass of the element ?

Ans: 20.2

22. What is the atomicity of ozone?

Ans: The atomicity of ozone is 2

23. Determine which molecule from the following elements is tetratomic?

(a) ozone (b) phosphorus (c) sulphur (d) xenon

Ans: Phosphorus

24. What is the number of significant figures in 6.023 x 1023 ?

Ans: The number of significant figures is  4

25. Determine the approximate number of atoms present in lg CH3COOH ?

Ans:  The approximate number of atoms present is 1022

26. Find the number of significant figures in 0.0480 ?

Ans: The number of significant figures is 3

27. Give the number of dimensionally independent physical quantities in SI units?

Ans: 7

28. Give the equivalent of 1 cm3 of volume?

Ans: 10-3 dm3

29. Determine the equivalent of one joule of energy ?

Ans:  0.2381 cal

30. From the following, determine the SI unit of work?

(a) cal (b) Joule (c) litre-atm (d) ergs

Ans: Joule

31. One kg weight is equivalent to

Ans:  9.8 N

32. The unit of J. Pa-I is equivalent to

Ans:  m3

33.  From the listed elements, determine which of the element is not an element?

(a) Diamond (b) 22 carat gold (c) graphite (d) oxygen

Ans: 22 carat gold

34.  From the given mixtures, find which one is not a homogeneous mixture?

(a) one rupee coin (b) gasoline (c) iodised table salt (d) air

Ans: Iodised table salt

35.  Give the mass of a Mg atom ?

Ans: The mass of Mg atom is 24.3/6.02 x 1023 g

36.  Determine the number of mols of carbon present in 1 mot of ethanol?

Ans:  2

37. 615.00 has...........significant figures

Ans: 5

38. How will you measure the Luminous intensity ?

Ans: The luminous intensity is measured in terms of Candela

39. The prefix tera means

Ans: 1012

40. Pure water can be obtained from sea water by which process?

Ans:  Distillation process

41. From the listed elements, find which one contains the largest number of molecules?

(a) 1g CO2  (b) 1g N2 (c) 1 g H2  (d) 1 g CH4

Ans:  1 g H2

42. Carbon forms two oxides CO and CO2. This illustrates which law?

Ans: Law of  Multiple proportions

43. Two oxides of a metal contain 50% and 60% of oxygen respectively. If the formula of the first oxide is MO, determine the formula of the second one?

Ans: The formula of the second one is M2O3

44. What is the simplest formula for a compound with 50% of element X (atomic mass 10) and 50% of element Y (atomic mass 20) in it?

Ans: The simplest formula is: X2Y

45. Which of the following contains the same number of atoms as in 6 g carbon?

(a) 24 g Mg  (b) 23 g Sodium  (c) 20 g Ca  (d) 63.5 g Cu

Ans: 20 g Ca

46. 3.2 g of gas contains 6.02 x 1022 molecules. determine its vapour density?

Ans: The vapour density is 16

47. Find the volume of 1 M NaOH required to convert 1.2 g of NaHSO4 completely to Na2SO4 ?

Ans: 10 ml

48. How many moles of water would be formed when 4 g of methane (CH4) are burnt?

Ans: 0.5

49. calculate the number of significant figures of the following numbers?

(a) 100.04

Ans: 5

(b) 4.20 x 1010

Ans: 3

(c) 324.0

Ans: 4

(d) 500.00

Ans: 5

(e) 0.02670

Ans: 4

50. Compute the following:

(a) 5.28 x 0.156 x 3/0.428

Ans: 5.77

(b) 5.28 x 0.156 x 3/0.421

Ans: 5.67

51.  List the proper number of significant figures in the following and indicate which zeros are significant?

(a) 0.216

Ans: 3 Significant figures

(b) 90.1

Ans: 3 Significant figures and zero is significant

(c) 800.0

Ans: 4 Significant figures all zeros are significant

(d) 0.0670

Ans: 3 Significant figures, last zero is significant

52.  Determine the number of moles of Oxygen atoms are there in

(a) one mole of HNO3

Ans: 3 moles

(b) one mole of H2SO4

Ans: 4 moles

53. Determine the number of moles of water produced when 8 g of methane (CH4) are burnt?

Ans: 1 mol.

54. How many moles of KClO3 are needed to give 1.5 moles of oxygen?

Ans: 1 mol.

55. How many moles of KCl are formed when 0.33 mol of KClO3 is decomposed?

Ans: 0.33 mol.

56. A chemist weighs 10 g of water, 10 g of ammonia and 10 g of hydrogen chloride. Calculate the total number of moles contained in the mixture?

Ans: 1.4 moles

57. Give the mass of a silver atom?

Ans: 1.794 x 10-22

58. Determine the number of molecules contained in a drop of water weighing 0.04 g?

Ans: 1.34 x 1021 molecules

59. Express 0.000000367 in scientific notation and calculate the significant figures?

Ans: 3.67 x 10-7 ; Number of significant figures is 3

60. What is the mass of HCl required to neutralise completely 5g  of NaOH?

Ans: 4.545 g

61. Which contains more molecules: 1 g of sulphur dioxide or 1 g of sulphur trioxide?

Ans: 1 g of SO2

## Helical Spring Experiment Viva Questions

Helical Spring Experiment Viva Questions and Answers

1. What is the principle of a spring?

Hooke's law

2. Define Hooke's law.

According to Hooke's law, within elastic limit, stress is directly proportional to strain.

i.e., Stress/ Strain =a constant

3. Define strain.

Strain = Change in dimension /Original dimension

4. Define stress.

It is the normal force acting per unit area

Stress = Restoring force/Area

5. What will you do so that the load attached to the one end of the spring oscillates in the vertical plane in order to obtain simple harmonic oscillations?

Spring should be suspended vertically and the amplitude of the oscillations should be small.

6. State the condition under which a spring obeys Hooke's law.

Extension of the spring should remain within elastic limit.

7. What are the forces acting on the load that is attached to the spring which is oscillating in a vertical plane?

The forces are weight and tension.

8. Define spring constant or force constant of a spring.

F = -kx; where k is the spring constant. It is the force required to produce unit extension on a spring.

9. What is the unit of force constant?

newton / metre (N/m)

10. What are the conditions essential for the motion of a body to be simple harmonic?

(a) acceleration is proportional to its distance from the fixed point
(b) acceleration is directed towards a fixed point

11. What are the factors on which the period of vertical oscillations of a spring depend?

(a) Directly proportional to the square root of the mass attached
(b) inversely proportional to the spring constant

12. What is the unit of spring constant?

Nm-1

13. Which is more elastic-steel wire or rubber wire of the same diameter and length?

Steel wire

14. What is the spring constant in terms of load (M) and extension (e)

K = Load / Extension = M/e kg/m = (M/e)gNm-1

15. Aim of Experiment.

To determine the spring constant by measuring the time period of vertical oscillations of a known load and to check the result by measuring the extension for a known force

16. Apparatus of Experiment.

A helical spring, Stand, Slotted weights, Stop-watch etc..

17. Principle of Experiment.

i. Vertical oscillations: The period of vertical oscillations of a helical spring is given by,

T = 2π(M/K)

K = 4π2(M/T2)

Where, K = spring constant, M = Total mass attached, T = Period of oscillations

ii. Load extension method: Using Hooke’s law, load is proportional to extension,

Spring constsnt, K = Load/Extension = mg/l

18. Procedure of Vertical Oscillations of Experiment

The given spring is suspended from a rigid support. A weight hanger with a dead load (w0) is suspended at the lower end of the spring (w0 should be sufficient to bring the spring in the elastic mood). A pointer is attached to the spring. The weight is slightly pulled down and released. The spring executes vertical oscillations. The time taken for 20 oscillations is noted and the period of oscillation (t/20) is calculated. Changing the loads [say (w0+w), (w0+2w),…..] and the period of oscillations are again determined. In each case M/T2 is calculated and hence its mean value is determined. A graph is plotted with M along the X-axis and T2 along, the Y-axis. The graph is found to be a straight line. From this K can also be calculated.

19. Procedure of Load-extension method of Experiment

The given spring is suspended from a rigid support. A pointer attached to the spring moves over a scale. Reading on the scale for w0, (w0+w), (w0+2w)…. are found. The mean value of scale reading for loading and unloading are r0, r1, r2 ….. respectively. Extension (l) for loads w, 2w, 3w …. Are given by (r1-r0), (r2-r0), (r3-r0) etc. are calculated. The spring constant,