
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).
8. Define adiabatic 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.
12. What is radiation?
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
Ans: The experimental wire is made taut by placing a suitable dead load Wo on the weight hanger attached to the lower end of the vernier. It is brought into elastic mood by repeatedly loading, and unloading.
With the dead weight W0 alone, the reading r0 of the vernier is taken. A suitable weight m, say 0.5 kg, is placed on the weight hanger over the dead load and the reading of the vernier is again taken. The experiment is repeated by adding load 2 m, 3 m, 4 m... over the dead load and the vernier is read in each case. The load are removed one by one and the vernier readings are again taken. The average readings r1, r2, r3, r4,... for the load (W0 + m), (W0 +2m) , (W0 +3m)(W0 +4m)…... are calculated. From these readings extensions for the loads M = m, 2m, 3m, 4m, …. are taken as (r1 — r0), (r2 — r0), (r3 — r0), (r4 — r0),…. A graph is drawn with extension along the Y-axis and load along the X-axis. The graph is a straight line. The reciprocal of its slope gives M/l, the load/extension of the wire.
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)
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,
K = Load/
Extension
A graph is
plotted with M along the X-axis and extension along the Y-axis. The graph is
found to be a straight line. From this K can also be calculated.